1//===- GlobalOpt.cpp - Optimize Global Variables --------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This pass transforms simple global variables that never have their address
10// taken. If obviously true, it marks read/write globals as constant, deletes
11// variables only stored to, etc.
12//
13//===----------------------------------------------------------------------===//
14
15#include "llvm/Transforms/IPO/GlobalOpt.h"
16#include "llvm/ADT/DenseMap.h"
17#include "llvm/ADT/STLExtras.h"
18#include "llvm/ADT/SmallPtrSet.h"
19#include "llvm/ADT/SmallVector.h"
20#include "llvm/ADT/Statistic.h"
21#include "llvm/ADT/Twine.h"
22#include "llvm/ADT/iterator_range.h"
23#include "llvm/Analysis/BlockFrequencyInfo.h"
24#include "llvm/Analysis/ConstantFolding.h"
25#include "llvm/Analysis/MemoryBuiltins.h"
26#include "llvm/Analysis/TargetLibraryInfo.h"
27#include "llvm/Analysis/TargetTransformInfo.h"
28#include "llvm/Analysis/ValueTracking.h"
29#include "llvm/BinaryFormat/Dwarf.h"
30#include "llvm/IR/Attributes.h"
31#include "llvm/IR/BasicBlock.h"
32#include "llvm/IR/CallingConv.h"
33#include "llvm/IR/Constant.h"
34#include "llvm/IR/Constants.h"
35#include "llvm/IR/DataLayout.h"
36#include "llvm/IR/DebugInfoMetadata.h"
37#include "llvm/IR/DerivedTypes.h"
38#include "llvm/IR/Dominators.h"
39#include "llvm/IR/Function.h"
40#include "llvm/IR/GlobalAlias.h"
41#include "llvm/IR/GlobalValue.h"
42#include "llvm/IR/GlobalVariable.h"
43#include "llvm/IR/IRBuilder.h"
44#include "llvm/IR/InstrTypes.h"
45#include "llvm/IR/Instruction.h"
46#include "llvm/IR/Instructions.h"
47#include "llvm/IR/IntrinsicInst.h"
48#include "llvm/IR/Module.h"
49#include "llvm/IR/Operator.h"
50#include "llvm/IR/ProfDataUtils.h"
51#include "llvm/IR/Type.h"
52#include "llvm/IR/Use.h"
53#include "llvm/IR/User.h"
54#include "llvm/IR/Value.h"
55#include "llvm/IR/ValueHandle.h"
56#include "llvm/Support/AtomicOrdering.h"
57#include "llvm/Support/Casting.h"
58#include "llvm/Support/CommandLine.h"
59#include "llvm/Support/Debug.h"
60#include "llvm/Support/ErrorHandling.h"
61#include "llvm/Support/raw_ostream.h"
62#include "llvm/Transforms/IPO.h"
63#include "llvm/Transforms/Utils/CtorUtils.h"
64#include "llvm/Transforms/Utils/Evaluator.h"
65#include "llvm/Transforms/Utils/GlobalStatus.h"
66#include "llvm/Transforms/Utils/Local.h"
67#include <cassert>
68#include <cstdint>
69#include <optional>
70#include <utility>
71#include <vector>
72
73using namespace llvm;
74
75#define DEBUG_TYPE "globalopt"
76
77STATISTIC(NumMarked , "Number of globals marked constant");
78STATISTIC(NumUnnamed , "Number of globals marked unnamed_addr");
79STATISTIC(NumSRA , "Number of aggregate globals broken into scalars");
80STATISTIC(NumSubstitute,"Number of globals with initializers stored into them");
81STATISTIC(NumDeleted , "Number of globals deleted");
82STATISTIC(NumGlobUses , "Number of global uses devirtualized");
83STATISTIC(NumLocalized , "Number of globals localized");
84STATISTIC(NumShrunkToBool , "Number of global vars shrunk to booleans");
85STATISTIC(NumFastCallFns , "Number of functions converted to fastcc");
86STATISTIC(NumCtorsEvaluated, "Number of static ctors evaluated");
87STATISTIC(NumNestRemoved , "Number of nest attributes removed");
88STATISTIC(NumAliasesResolved, "Number of global aliases resolved");
89STATISTIC(NumAliasesRemoved, "Number of global aliases eliminated");
90STATISTIC(NumCXXDtorsRemoved, "Number of global C++ destructors removed");
91STATISTIC(NumAtExitRemoved, "Number of atexit handlers removed");
92STATISTIC(NumInternalFunc, "Number of internal functions");
93STATISTIC(NumColdCC, "Number of functions marked coldcc");
94STATISTIC(NumIFuncsResolved, "Number of statically resolved IFuncs");
95STATISTIC(NumIFuncsDeleted, "Number of IFuncs removed");
96
97static cl::opt<bool>
98 OptimizeNonFMVCallers("optimize-non-fmv-callers",
99 cl::desc("Statically resolve calls to versioned "
100 "functions from non-versioned callers."),
101 cl::init(Val: true), cl::Hidden);
102
103static cl::opt<unsigned> MaxIFuncVersions(
104 "max-ifunc-versions", cl::Hidden, cl::init(Val: 5),
105 cl::desc("Maximum number of caller/callee versions that is allowed for "
106 "using the expensive (cubic) static resolution algorithm."));
107
108static cl::opt<bool>
109 EnableColdCCStressTest("enable-coldcc-stress-test",
110 cl::desc("Enable stress test of coldcc by adding "
111 "calling conv to all internal functions."),
112 cl::init(Val: false), cl::Hidden);
113
114static cl::opt<int> ColdCCRelFreq(
115 "coldcc-rel-freq", cl::Hidden, cl::init(Val: 2),
116 cl::desc(
117 "Maximum block frequency, expressed as a percentage of caller's "
118 "entry frequency, for a call site to be considered cold for enabling "
119 "coldcc"));
120
121/// Is this global variable possibly used by a leak checker as a root? If so,
122/// we might not really want to eliminate the stores to it.
123static bool isLeakCheckerRoot(GlobalVariable *GV) {
124 // A global variable is a root if it is a pointer, or could plausibly contain
125 // a pointer. There are two challenges; one is that we could have a struct
126 // the has an inner member which is a pointer. We recurse through the type to
127 // detect these (up to a point). The other is that we may actually be a union
128 // of a pointer and another type, and so our LLVM type is an integer which
129 // gets converted into a pointer, or our type is an [i8 x #] with a pointer
130 // potentially contained here.
131
132 if (GV->hasPrivateLinkage())
133 return false;
134
135 SmallVector<Type *, 4> Types;
136 Types.push_back(Elt: GV->getValueType());
137
138 unsigned Limit = 20;
139 do {
140 Type *Ty = Types.pop_back_val();
141 switch (Ty->getTypeID()) {
142 default: break;
143 case Type::PointerTyID:
144 return true;
145 case Type::FixedVectorTyID:
146 case Type::ScalableVectorTyID:
147 if (cast<VectorType>(Val: Ty)->getElementType()->isPointerTy())
148 return true;
149 break;
150 case Type::ArrayTyID:
151 Types.push_back(Elt: cast<ArrayType>(Val: Ty)->getElementType());
152 break;
153 case Type::StructTyID: {
154 StructType *STy = cast<StructType>(Val: Ty);
155 if (STy->isOpaque()) return true;
156 for (Type *InnerTy : STy->elements()) {
157 if (isa<PointerType>(Val: InnerTy)) return true;
158 if (isa<StructType>(Val: InnerTy) || isa<ArrayType>(Val: InnerTy) ||
159 isa<VectorType>(Val: InnerTy))
160 Types.push_back(Elt: InnerTy);
161 }
162 break;
163 }
164 }
165 if (--Limit == 0) return true;
166 } while (!Types.empty());
167 return false;
168}
169
170/// Given a value that is stored to a global but never read, determine whether
171/// it's safe to remove the store and the chain of computation that feeds the
172/// store.
173static bool IsSafeComputationToRemove(
174 Value *V, function_ref<TargetLibraryInfo &(Function &)> GetTLI) {
175 do {
176 if (isa<Constant>(Val: V))
177 return true;
178 if (!V->hasOneUse())
179 return false;
180 if (isa<LoadInst>(Val: V) || isa<InvokeInst>(Val: V) || isa<Argument>(Val: V) ||
181 isa<GlobalValue>(Val: V))
182 return false;
183 if (isAllocationFn(V, GetTLI))
184 return true;
185
186 Instruction *I = cast<Instruction>(Val: V);
187 if (I->mayHaveSideEffects())
188 return false;
189 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Val: I)) {
190 if (!GEP->hasAllConstantIndices())
191 return false;
192 } else if (I->getNumOperands() != 1) {
193 return false;
194 }
195
196 V = I->getOperand(i: 0);
197 } while (true);
198}
199
200/// This GV is a pointer root. Loop over all users of the global and clean up
201/// any that obviously don't assign the global a value that isn't dynamically
202/// allocated.
203static bool
204CleanupPointerRootUsers(GlobalVariable *GV,
205 function_ref<TargetLibraryInfo &(Function &)> GetTLI) {
206 // A brief explanation of leak checkers. The goal is to find bugs where
207 // pointers are forgotten, causing an accumulating growth in memory
208 // usage over time. The common strategy for leak checkers is to explicitly
209 // allow the memory pointed to by globals at exit. This is popular because it
210 // also solves another problem where the main thread of a C++ program may shut
211 // down before other threads that are still expecting to use those globals. To
212 // handle that case, we expect the program may create a singleton and never
213 // destroy it.
214
215 bool Changed = false;
216
217 // If Dead[n].first is the only use of a malloc result, we can delete its
218 // chain of computation and the store to the global in Dead[n].second.
219 SmallVector<std::pair<Instruction *, Instruction *>, 32> Dead;
220
221 SmallVector<User *> Worklist(GV->users());
222 // Constants can't be pointers to dynamically allocated memory.
223 while (!Worklist.empty()) {
224 User *U = Worklist.pop_back_val();
225 if (StoreInst *SI = dyn_cast<StoreInst>(Val: U)) {
226 Value *V = SI->getValueOperand();
227 if (isa<Constant>(Val: V)) {
228 Changed = true;
229 SI->eraseFromParent();
230 } else if (Instruction *I = dyn_cast<Instruction>(Val: V)) {
231 if (I->hasOneUse())
232 Dead.push_back(Elt: std::make_pair(x&: I, y&: SI));
233 }
234 } else if (MemSetInst *MSI = dyn_cast<MemSetInst>(Val: U)) {
235 if (isa<Constant>(Val: MSI->getValue())) {
236 Changed = true;
237 MSI->eraseFromParent();
238 } else if (Instruction *I = dyn_cast<Instruction>(Val: MSI->getValue())) {
239 if (I->hasOneUse())
240 Dead.push_back(Elt: std::make_pair(x&: I, y&: MSI));
241 }
242 } else if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(Val: U)) {
243 GlobalVariable *MemSrc = dyn_cast<GlobalVariable>(Val: MTI->getSource());
244 if (MemSrc && MemSrc->isConstant()) {
245 Changed = true;
246 MTI->eraseFromParent();
247 } else if (Instruction *I = dyn_cast<Instruction>(Val: MTI->getSource())) {
248 if (I->hasOneUse())
249 Dead.push_back(Elt: std::make_pair(x&: I, y&: MTI));
250 }
251 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Val: U)) {
252 if (isa<GEPOperator>(Val: CE))
253 append_range(C&: Worklist, R: CE->users());
254 }
255 }
256
257 for (const auto &[Inst, Store] : Dead) {
258 if (IsSafeComputationToRemove(V: Inst, GetTLI)) {
259 Store->eraseFromParent();
260 Instruction *I = Inst;
261 do {
262 if (isAllocationFn(V: I, GetTLI))
263 break;
264 Instruction *J = dyn_cast<Instruction>(Val: I->getOperand(i: 0));
265 if (!J)
266 break;
267 I->eraseFromParent();
268 I = J;
269 } while (true);
270 I->eraseFromParent();
271 Changed = true;
272 }
273 }
274
275 GV->removeDeadConstantUsers();
276 return Changed;
277}
278
279/// We just marked GV constant. Loop over all users of the global, cleaning up
280/// the obvious ones. This is largely just a quick scan over the use list to
281/// clean up the easy and obvious cruft. This returns true if it made a change.
282static bool CleanupConstantGlobalUsers(GlobalVariable *GV,
283 const DataLayout &DL) {
284 Constant *Init = GV->getInitializer();
285 SmallVector<User *, 8> WorkList(GV->users());
286 SmallPtrSet<User *, 8> Visited;
287 bool Changed = false;
288
289 SmallVector<WeakTrackingVH> MaybeDeadInsts;
290 auto EraseFromParent = [&](Instruction *I) {
291 for (Value *Op : I->operands())
292 if (auto *OpI = dyn_cast<Instruction>(Val: Op))
293 MaybeDeadInsts.push_back(Elt: OpI);
294 I->eraseFromParent();
295 Changed = true;
296 };
297 while (!WorkList.empty()) {
298 User *U = WorkList.pop_back_val();
299 if (!Visited.insert(Ptr: U).second)
300 continue;
301
302 if (auto *BO = dyn_cast<BitCastOperator>(Val: U))
303 append_range(C&: WorkList, R: BO->users());
304 if (auto *ASC = dyn_cast<AddrSpaceCastOperator>(Val: U))
305 append_range(C&: WorkList, R: ASC->users());
306 else if (auto *GEP = dyn_cast<GEPOperator>(Val: U))
307 append_range(C&: WorkList, R: GEP->users());
308 else if (auto *LI = dyn_cast<LoadInst>(Val: U)) {
309 // A load from a uniform value is always the same, regardless of any
310 // applied offset.
311 Type *Ty = LI->getType();
312 if (Constant *Res = ConstantFoldLoadFromUniformValue(C: Init, Ty, DL)) {
313 LI->replaceAllUsesWith(V: Res);
314 EraseFromParent(LI);
315 continue;
316 }
317
318 Value *PtrOp = LI->getPointerOperand();
319 APInt Offset(DL.getIndexTypeSizeInBits(Ty: PtrOp->getType()), 0);
320 PtrOp = PtrOp->stripAndAccumulateConstantOffsets(
321 DL, Offset, /* AllowNonInbounds */ true);
322 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Val: PtrOp)) {
323 if (II->getIntrinsicID() == Intrinsic::threadlocal_address)
324 PtrOp = II->getArgOperand(i: 0);
325 }
326 if (PtrOp == GV) {
327 if (auto *Value = ConstantFoldLoadFromConst(C: Init, Ty, Offset, DL)) {
328 LI->replaceAllUsesWith(V: Value);
329 EraseFromParent(LI);
330 }
331 }
332 } else if (StoreInst *SI = dyn_cast<StoreInst>(Val: U)) {
333 // Store must be unreachable or storing Init into the global.
334 EraseFromParent(SI);
335 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(Val: U)) { // memset/cpy/mv
336 if (getUnderlyingObject(V: MI->getRawDest()) == GV)
337 EraseFromParent(MI);
338 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Val: U)) {
339 if (II->getIntrinsicID() == Intrinsic::threadlocal_address)
340 append_range(C&: WorkList, R: II->users());
341 }
342 }
343
344 Changed |=
345 RecursivelyDeleteTriviallyDeadInstructionsPermissive(DeadInsts&: MaybeDeadInsts);
346 GV->removeDeadConstantUsers();
347 return Changed;
348}
349
350/// Part of the global at a specific offset, which is only accessed through
351/// loads and stores with the given type.
352struct GlobalPart {
353 Type *Ty;
354 Constant *Initializer = nullptr;
355 bool IsLoaded = false;
356 bool IsStored = false;
357};
358
359/// Look at all uses of the global and determine which (offset, type) pairs it
360/// can be split into.
361static bool collectSRATypes(DenseMap<uint64_t, GlobalPart> &Parts,
362 GlobalVariable *GV, const DataLayout &DL) {
363 SmallVector<Use *, 16> Worklist;
364 SmallPtrSet<Use *, 16> Visited;
365 auto AppendUses = [&](Value *V) {
366 for (Use &U : V->uses())
367 if (Visited.insert(Ptr: &U).second)
368 Worklist.push_back(Elt: &U);
369 };
370 AppendUses(GV);
371 while (!Worklist.empty()) {
372 Use *U = Worklist.pop_back_val();
373 User *V = U->getUser();
374
375 auto *GEP = dyn_cast<GEPOperator>(Val: V);
376 if (isa<BitCastOperator>(Val: V) || isa<AddrSpaceCastOperator>(Val: V) ||
377 (GEP && GEP->hasAllConstantIndices())) {
378 AppendUses(V);
379 continue;
380 }
381
382 if (Value *Ptr = getLoadStorePointerOperand(V)) {
383 // This is storing the global address into somewhere, not storing into
384 // the global.
385 if (isa<StoreInst>(Val: V) && U->getOperandNo() == 0)
386 return false;
387
388 APInt Offset(DL.getIndexTypeSizeInBits(Ty: Ptr->getType()), 0);
389 Ptr = Ptr->stripAndAccumulateConstantOffsets(DL, Offset,
390 /* AllowNonInbounds */ true);
391 if (Ptr != GV || Offset.getActiveBits() >= 64)
392 return false;
393
394 // TODO: We currently require that all accesses at a given offset must
395 // use the same type. This could be relaxed.
396 Type *Ty = getLoadStoreType(I: V);
397 const auto &[It, Inserted] =
398 Parts.try_emplace(Key: Offset.getZExtValue(), Args: GlobalPart{.Ty: Ty});
399 if (Ty != It->second.Ty)
400 return false;
401
402 if (Inserted) {
403 It->second.Initializer =
404 ConstantFoldLoadFromConst(C: GV->getInitializer(), Ty, Offset, DL);
405 if (!It->second.Initializer) {
406 LLVM_DEBUG(dbgs() << "Global SRA: Failed to evaluate initializer of "
407 << *GV << " with type " << *Ty << " at offset "
408 << Offset.getZExtValue());
409 return false;
410 }
411 }
412
413 // Scalable types not currently supported.
414 if (Ty->isScalableTy())
415 return false;
416
417 auto IsStored = [](Value *V, Constant *Initializer) {
418 auto *SI = dyn_cast<StoreInst>(Val: V);
419 if (!SI)
420 return false;
421
422 Constant *StoredConst = dyn_cast<Constant>(Val: SI->getOperand(i_nocapture: 0));
423 if (!StoredConst)
424 return true;
425
426 // Don't consider stores that only write the initializer value.
427 return Initializer != StoredConst;
428 };
429
430 It->second.IsLoaded |= isa<LoadInst>(Val: V);
431 It->second.IsStored |= IsStored(V, It->second.Initializer);
432 continue;
433 }
434
435 // Ignore dead constant users.
436 if (auto *C = dyn_cast<Constant>(Val: V)) {
437 if (!isSafeToDestroyConstant(C))
438 return false;
439 continue;
440 }
441
442 // Unknown user.
443 return false;
444 }
445
446 return true;
447}
448
449/// Copy over the debug info for a variable to its SRA replacements.
450static void transferSRADebugInfo(GlobalVariable *GV, GlobalVariable *NGV,
451 uint64_t FragmentOffsetInBits,
452 uint64_t FragmentSizeInBits,
453 uint64_t VarSize) {
454 SmallVector<DIGlobalVariableExpression *, 1> GVs;
455 GV->getDebugInfo(GVs);
456 for (auto *GVE : GVs) {
457 DIVariable *Var = GVE->getVariable();
458 DIExpression *Expr = GVE->getExpression();
459 int64_t CurVarOffsetInBytes = 0;
460 uint64_t CurVarOffsetInBits = 0;
461 uint64_t FragmentEndInBits = FragmentOffsetInBits + FragmentSizeInBits;
462
463 // Calculate the offset (Bytes), Continue if unknown.
464 if (!Expr->extractIfOffset(Offset&: CurVarOffsetInBytes))
465 continue;
466
467 // Ignore negative offset.
468 if (CurVarOffsetInBytes < 0)
469 continue;
470
471 // Convert offset to bits.
472 CurVarOffsetInBits = CHAR_BIT * (uint64_t)CurVarOffsetInBytes;
473
474 // Current var starts after the fragment, ignore.
475 if (CurVarOffsetInBits >= FragmentEndInBits)
476 continue;
477
478 uint64_t CurVarSize = Var->getType()->getSizeInBits();
479 uint64_t CurVarEndInBits = CurVarOffsetInBits + CurVarSize;
480 // Current variable ends before start of fragment, ignore.
481 if (CurVarSize != 0 && /* CurVarSize is known */
482 CurVarEndInBits <= FragmentOffsetInBits)
483 continue;
484
485 // Current variable fits in (not greater than) the fragment,
486 // does not need fragment expression.
487 if (CurVarSize != 0 && /* CurVarSize is known */
488 CurVarOffsetInBits >= FragmentOffsetInBits &&
489 CurVarEndInBits <= FragmentEndInBits) {
490 uint64_t CurVarOffsetInFragment =
491 (CurVarOffsetInBits - FragmentOffsetInBits) / 8;
492 if (CurVarOffsetInFragment != 0)
493 Expr = DIExpression::get(Context&: Expr->getContext(), Elements: {dwarf::DW_OP_plus_uconst,
494 CurVarOffsetInFragment});
495 else
496 Expr = DIExpression::get(Context&: Expr->getContext(), Elements: {});
497 auto *NGVE =
498 DIGlobalVariableExpression::get(Context&: GVE->getContext(), Variable: Var, Expression: Expr);
499 NGV->addDebugInfo(GV: NGVE);
500 continue;
501 }
502 // Current variable does not fit in single fragment,
503 // emit a fragment expression.
504 if (FragmentSizeInBits < VarSize) {
505 if (CurVarOffsetInBits > FragmentOffsetInBits)
506 continue;
507 uint64_t CurVarFragmentOffsetInBits =
508 FragmentOffsetInBits - CurVarOffsetInBits;
509 uint64_t CurVarFragmentSizeInBits = FragmentSizeInBits;
510 if (CurVarSize != 0 && CurVarEndInBits < FragmentEndInBits)
511 CurVarFragmentSizeInBits -= (FragmentEndInBits - CurVarEndInBits);
512 if (CurVarOffsetInBits)
513 Expr = DIExpression::get(Context&: Expr->getContext(), Elements: {});
514 if (auto E = DIExpression::createFragmentExpression(
515 Expr, OffsetInBits: CurVarFragmentOffsetInBits, SizeInBits: CurVarFragmentSizeInBits))
516 Expr = *E;
517 else
518 continue;
519 }
520 auto *NGVE = DIGlobalVariableExpression::get(Context&: GVE->getContext(), Variable: Var, Expression: Expr);
521 NGV->addDebugInfo(GV: NGVE);
522 }
523}
524
525/// Perform scalar replacement of aggregates on the specified global variable.
526/// This opens the door for other optimizations by exposing the behavior of the
527/// program in a more fine-grained way. We have determined that this
528/// transformation is safe already. We return the first global variable we
529/// insert so that the caller can reprocess it.
530static GlobalVariable *SRAGlobal(GlobalVariable *GV, const DataLayout &DL) {
531 assert(GV->hasLocalLinkage());
532
533 // Collect types to split into.
534 DenseMap<uint64_t, GlobalPart> Parts;
535 if (!collectSRATypes(Parts, GV, DL) || Parts.empty())
536 return nullptr;
537
538 // Make sure we don't SRA back to the same type.
539 if (Parts.size() == 1 && Parts.begin()->second.Ty == GV->getValueType())
540 return nullptr;
541
542 // Don't perform SRA if we would have to split into many globals. Ignore
543 // parts that are either only loaded or only stored, because we expect them
544 // to be optimized away.
545 unsigned NumParts = count_if(Range&: Parts, P: [](const auto &Pair) {
546 return Pair.second.IsLoaded && Pair.second.IsStored;
547 });
548 if (NumParts > 16)
549 return nullptr;
550
551 // Sort by offset.
552 SmallVector<std::tuple<uint64_t, Type *, Constant *>, 16> TypesVector;
553 for (const auto &Pair : Parts) {
554 TypesVector.push_back(
555 Elt: {Pair.first, Pair.second.Ty, Pair.second.Initializer});
556 }
557 sort(C&: TypesVector, Comp: llvm::less_first());
558
559 // Check that the types are non-overlapping.
560 uint64_t Offset = 0;
561 for (const auto &[OffsetForTy, Ty, _] : TypesVector) {
562 // Overlaps with previous type.
563 if (OffsetForTy < Offset)
564 return nullptr;
565
566 Offset = OffsetForTy + DL.getTypeAllocSize(Ty);
567 }
568
569 // Some accesses go beyond the end of the global, don't bother.
570 if (Offset > GV->getGlobalSize(DL))
571 return nullptr;
572
573 LLVM_DEBUG(dbgs() << "PERFORMING GLOBAL SRA ON: " << *GV << "\n");
574
575 // Get the alignment of the global, either explicit or target-specific.
576 Align StartAlignment =
577 DL.getValueOrABITypeAlignment(Alignment: GV->getAlign(), Ty: GV->getValueType());
578 uint64_t VarSize = DL.getTypeSizeInBits(Ty: GV->getValueType());
579
580 // Create replacement globals.
581 DenseMap<uint64_t, GlobalVariable *> NewGlobals;
582 unsigned NameSuffix = 0;
583 for (auto &[OffsetForTy, Ty, Initializer] : TypesVector) {
584 GlobalVariable *NGV = new GlobalVariable(
585 *GV->getParent(), Ty, false, GlobalVariable::InternalLinkage,
586 Initializer, GV->getName() + "." + Twine(NameSuffix++), GV,
587 GV->getThreadLocalMode(), GV->getAddressSpace());
588 // Start out by copying attributes from the original, including alignment.
589 NGV->copyAttributesFrom(Src: GV);
590 NewGlobals.insert(KV: {OffsetForTy, NGV});
591
592 // Calculate the known alignment of the field. If the original aggregate
593 // had 256 byte alignment for example, then the element at a given offset
594 // may also have a known alignment, and something might depend on that:
595 // propagate info to each field.
596 Align NewAlign = commonAlignment(A: StartAlignment, Offset: OffsetForTy);
597 NGV->setAlignment(NewAlign);
598
599 // Copy over the debug info for the variable.
600 transferSRADebugInfo(GV, NGV, FragmentOffsetInBits: OffsetForTy * 8,
601 FragmentSizeInBits: DL.getTypeAllocSizeInBits(Ty), VarSize);
602 }
603
604 // Replace uses of the original global with uses of the new global.
605 SmallVector<Value *, 16> Worklist;
606 SmallPtrSet<Value *, 16> Visited;
607 SmallVector<WeakTrackingVH, 16> DeadInsts;
608 auto AppendUsers = [&](Value *V) {
609 for (User *U : V->users())
610 if (Visited.insert(Ptr: U).second)
611 Worklist.push_back(Elt: U);
612 };
613 AppendUsers(GV);
614 while (!Worklist.empty()) {
615 Value *V = Worklist.pop_back_val();
616 if (isa<BitCastOperator>(Val: V) || isa<AddrSpaceCastOperator>(Val: V) ||
617 isa<GEPOperator>(Val: V)) {
618 AppendUsers(V);
619 if (isa<Instruction>(Val: V))
620 DeadInsts.push_back(Elt: V);
621 continue;
622 }
623
624 if (Value *Ptr = getLoadStorePointerOperand(V)) {
625 APInt Offset(DL.getIndexTypeSizeInBits(Ty: Ptr->getType()), 0);
626 Ptr = Ptr->stripAndAccumulateConstantOffsets(DL, Offset,
627 /* AllowNonInbounds */ true);
628 assert(Ptr == GV && "Load/store must be from/to global");
629 GlobalVariable *NGV = NewGlobals[Offset.getZExtValue()];
630 assert(NGV && "Must have replacement global for this offset");
631
632 // Update the pointer operand and recalculate alignment.
633 Align PrefAlign = DL.getPrefTypeAlign(Ty: getLoadStoreType(I: V));
634 Align NewAlign =
635 getOrEnforceKnownAlignment(V: NGV, PrefAlign, DL, CxtI: cast<Instruction>(Val: V));
636
637 if (auto *LI = dyn_cast<LoadInst>(Val: V)) {
638 LI->setOperand(i_nocapture: 0, Val_nocapture: NGV);
639 LI->setAlignment(NewAlign);
640 } else {
641 auto *SI = cast<StoreInst>(Val: V);
642 SI->setOperand(i_nocapture: 1, Val_nocapture: NGV);
643 SI->setAlignment(NewAlign);
644 }
645 continue;
646 }
647
648 assert(isa<Constant>(V) && isSafeToDestroyConstant(cast<Constant>(V)) &&
649 "Other users can only be dead constants");
650 }
651
652 // Delete old instructions and global.
653 RecursivelyDeleteTriviallyDeadInstructions(DeadInsts);
654 GV->removeDeadConstantUsers();
655 GV->eraseFromParent();
656 ++NumSRA;
657
658 assert(NewGlobals.size() > 0);
659 return NewGlobals.begin()->second;
660}
661
662/// Return true if all users of the specified value will trap if the value is
663/// dynamically null. PHIs keeps track of any phi nodes we've seen to avoid
664/// reprocessing them.
665static bool AllUsesOfValueWillTrapIfNull(const Value *V,
666 SmallPtrSetImpl<const PHINode*> &PHIs) {
667 for (const User *U : V->users()) {
668 if (const Instruction *I = dyn_cast<Instruction>(Val: U)) {
669 // If null pointer is considered valid, then all uses are non-trapping.
670 // Non address-space 0 globals have already been pruned by the caller.
671 if (NullPointerIsDefined(F: I->getFunction()))
672 return false;
673 }
674 if (isa<LoadInst>(Val: U)) {
675 // Will trap.
676 } else if (const StoreInst *SI = dyn_cast<StoreInst>(Val: U)) {
677 if (SI->getOperand(i_nocapture: 0) == V) {
678 return false; // Storing the value.
679 }
680 } else if (const CallInst *CI = dyn_cast<CallInst>(Val: U)) {
681 if (CI->getCalledOperand() != V) {
682 return false; // Not calling the ptr
683 }
684 } else if (const InvokeInst *II = dyn_cast<InvokeInst>(Val: U)) {
685 if (II->getCalledOperand() != V) {
686 return false; // Not calling the ptr
687 }
688 } else if (const AddrSpaceCastInst *CI = dyn_cast<AddrSpaceCastInst>(Val: U)) {
689 if (!AllUsesOfValueWillTrapIfNull(V: CI, PHIs))
690 return false;
691 } else if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Val: U)) {
692 if (!AllUsesOfValueWillTrapIfNull(V: GEPI, PHIs)) return false;
693 } else if (const PHINode *PN = dyn_cast<PHINode>(Val: U)) {
694 // If we've already seen this phi node, ignore it, it has already been
695 // checked.
696 if (PHIs.insert(Ptr: PN).second && !AllUsesOfValueWillTrapIfNull(V: PN, PHIs))
697 return false;
698 } else if (isa<ICmpInst>(Val: U) &&
699 !ICmpInst::isSigned(predicate: cast<ICmpInst>(Val: U)->getPredicate()) &&
700 isa<LoadInst>(Val: U->getOperand(i: 0)) &&
701 isa<ConstantPointerNull>(Val: U->getOperand(i: 1))) {
702 assert(isa<GlobalValue>(cast<LoadInst>(U->getOperand(0))
703 ->getPointerOperand()
704 ->stripPointerCasts()) &&
705 "Should be GlobalVariable");
706 // This and only this kind of non-signed ICmpInst is to be replaced with
707 // the comparing of the value of the created global init bool later in
708 // optimizeGlobalAddressOfAllocation for the global variable.
709 } else {
710 return false;
711 }
712 }
713 return true;
714}
715
716/// Return true if all uses of any loads from GV will trap if the loaded value
717/// is null. Note that this also permits comparisons of the loaded value
718/// against null, as a special case.
719static bool allUsesOfLoadedValueWillTrapIfNull(const GlobalVariable *GV) {
720 SmallVector<const Value *, 4> Worklist;
721 Worklist.push_back(Elt: GV);
722 while (!Worklist.empty()) {
723 const Value *P = Worklist.pop_back_val();
724 for (const auto *U : P->users()) {
725 if (auto *LI = dyn_cast<LoadInst>(Val: U)) {
726 if (!LI->isSimple())
727 return false;
728 SmallPtrSet<const PHINode *, 8> PHIs;
729 if (!AllUsesOfValueWillTrapIfNull(V: LI, PHIs))
730 return false;
731 } else if (auto *SI = dyn_cast<StoreInst>(Val: U)) {
732 if (!SI->isSimple())
733 return false;
734 // Ignore stores to the global.
735 if (SI->getPointerOperand() != P)
736 return false;
737 } else if (auto *CE = dyn_cast<ConstantExpr>(Val: U)) {
738 if (CE->stripPointerCasts() != GV)
739 return false;
740 // Check further the ConstantExpr.
741 Worklist.push_back(Elt: CE);
742 } else {
743 // We don't know or understand this user, bail out.
744 return false;
745 }
746 }
747 }
748
749 return true;
750}
751
752/// Get all the loads/store uses for global variable \p GV.
753static void allUsesOfLoadAndStores(GlobalVariable *GV,
754 SmallVector<Value *, 4> &Uses) {
755 SmallVector<Value *, 4> Worklist;
756 Worklist.push_back(Elt: GV);
757 while (!Worklist.empty()) {
758 auto *P = Worklist.pop_back_val();
759 for (auto *U : P->users()) {
760 if (auto *CE = dyn_cast<ConstantExpr>(Val: U)) {
761 Worklist.push_back(Elt: CE);
762 continue;
763 }
764
765 assert((isa<LoadInst>(U) || isa<StoreInst>(U)) &&
766 "Expect only load or store instructions");
767 Uses.push_back(Elt: U);
768 }
769 }
770}
771
772static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) {
773 bool Changed = false;
774 for (auto UI = V->user_begin(), E = V->user_end(); UI != E; ) {
775 Instruction *I = cast<Instruction>(Val: *UI++);
776 // Uses are non-trapping if null pointer is considered valid.
777 // Non address-space 0 globals are already pruned by the caller.
778 if (NullPointerIsDefined(F: I->getFunction()))
779 return false;
780 if (LoadInst *LI = dyn_cast<LoadInst>(Val: I)) {
781 LI->setOperand(i_nocapture: 0, Val_nocapture: NewV);
782 Changed = true;
783 } else if (StoreInst *SI = dyn_cast<StoreInst>(Val: I)) {
784 if (SI->getOperand(i_nocapture: 1) == V) {
785 SI->setOperand(i_nocapture: 1, Val_nocapture: NewV);
786 Changed = true;
787 }
788 } else if (isa<CallInst>(Val: I) || isa<InvokeInst>(Val: I)) {
789 CallBase *CB = cast<CallBase>(Val: I);
790 if (CB->getCalledOperand() == V) {
791 // Calling through the pointer! Turn into a direct call, but be careful
792 // that the pointer is not also being passed as an argument.
793 CB->setCalledOperand(NewV);
794 Changed = true;
795 bool PassedAsArg = false;
796 for (unsigned i = 0, e = CB->arg_size(); i != e; ++i)
797 if (CB->getArgOperand(i) == V) {
798 PassedAsArg = true;
799 CB->setArgOperand(i, v: NewV);
800 }
801
802 if (PassedAsArg) {
803 // Being passed as an argument also. Be careful to not invalidate UI!
804 UI = V->user_begin();
805 }
806 }
807 } else if (AddrSpaceCastInst *CI = dyn_cast<AddrSpaceCastInst>(Val: I)) {
808 Changed |= OptimizeAwayTrappingUsesOfValue(
809 V: CI, NewV: ConstantExpr::getAddrSpaceCast(C: NewV, Ty: CI->getType()));
810 if (CI->use_empty()) {
811 Changed = true;
812 CI->eraseFromParent();
813 }
814 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Val: I)) {
815 // Should handle GEP here.
816 SmallVector<Constant*, 8> Idxs;
817 Idxs.reserve(N: GEPI->getNumOperands()-1);
818 for (User::op_iterator i = GEPI->op_begin() + 1, e = GEPI->op_end();
819 i != e; ++i)
820 if (Constant *C = dyn_cast<Constant>(Val&: *i))
821 Idxs.push_back(Elt: C);
822 else
823 break;
824 if (Idxs.size() == GEPI->getNumOperands()-1)
825 Changed |= OptimizeAwayTrappingUsesOfValue(
826 V: GEPI, NewV: ConstantExpr::getGetElementPtr(Ty: GEPI->getSourceElementType(),
827 C: NewV, IdxList: Idxs));
828 if (GEPI->use_empty()) {
829 Changed = true;
830 GEPI->eraseFromParent();
831 }
832 }
833 }
834
835 return Changed;
836}
837
838/// The specified global has only one non-null value stored into it. If there
839/// are uses of the loaded value that would trap if the loaded value is
840/// dynamically null, then we know that they cannot be reachable with a null
841/// optimize away the load.
842static bool OptimizeAwayTrappingUsesOfLoads(
843 GlobalVariable *GV, Constant *LV, const DataLayout &DL,
844 function_ref<TargetLibraryInfo &(Function &)> GetTLI) {
845 bool Changed = false;
846
847 // Keep track of whether we are able to remove all the uses of the global
848 // other than the store that defines it.
849 bool AllNonStoreUsesGone = true;
850
851 // Replace all uses of loads with uses of uses of the stored value.
852 for (User *GlobalUser : llvm::make_early_inc_range(Range: GV->users())) {
853 if (LoadInst *LI = dyn_cast<LoadInst>(Val: GlobalUser)) {
854 Changed |= OptimizeAwayTrappingUsesOfValue(V: LI, NewV: LV);
855 // If we were able to delete all uses of the loads
856 if (LI->use_empty()) {
857 LI->eraseFromParent();
858 Changed = true;
859 } else {
860 AllNonStoreUsesGone = false;
861 }
862 } else if (isa<StoreInst>(Val: GlobalUser)) {
863 // Ignore the store that stores "LV" to the global.
864 assert(GlobalUser->getOperand(1) == GV &&
865 "Must be storing *to* the global");
866 } else {
867 AllNonStoreUsesGone = false;
868
869 // If we get here we could have other crazy uses that are transitively
870 // loaded.
871 assert((isa<PHINode>(GlobalUser) || isa<SelectInst>(GlobalUser) ||
872 isa<ConstantExpr>(GlobalUser) || isa<CmpInst>(GlobalUser) ||
873 isa<BitCastInst>(GlobalUser) ||
874 isa<GetElementPtrInst>(GlobalUser) ||
875 isa<AddrSpaceCastInst>(GlobalUser)) &&
876 "Only expect load and stores!");
877 }
878 }
879
880 if (Changed) {
881 LLVM_DEBUG(dbgs() << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV
882 << "\n");
883 ++NumGlobUses;
884 }
885
886 // If we nuked all of the loads, then none of the stores are needed either,
887 // nor is the global.
888 if (AllNonStoreUsesGone) {
889 if (isLeakCheckerRoot(GV)) {
890 Changed |= CleanupPointerRootUsers(GV, GetTLI);
891 } else {
892 Changed = true;
893 CleanupConstantGlobalUsers(GV, DL);
894 }
895 if (GV->use_empty()) {
896 LLVM_DEBUG(dbgs() << " *** GLOBAL NOW DEAD!\n");
897 Changed = true;
898 GV->eraseFromParent();
899 ++NumDeleted;
900 }
901 }
902 return Changed;
903}
904
905/// Walk the use list of V, constant folding all of the instructions that are
906/// foldable.
907static void ConstantPropUsersOf(Value *V, const DataLayout &DL,
908 TargetLibraryInfo *TLI) {
909 for (Value::user_iterator UI = V->user_begin(), E = V->user_end(); UI != E; )
910 if (Instruction *I = dyn_cast<Instruction>(Val: *UI++))
911 if (Constant *NewC = ConstantFoldInstruction(I, DL, TLI)) {
912 I->replaceAllUsesWith(V: NewC);
913
914 // Advance UI to the next non-I use to avoid invalidating it!
915 // Instructions could multiply use V.
916 while (UI != E && *UI == I)
917 ++UI;
918 if (isInstructionTriviallyDead(I, TLI))
919 I->eraseFromParent();
920 }
921}
922
923/// This function takes the specified global variable, and transforms the
924/// program as if it always contained the result of the specified malloc.
925/// Because it is always the result of the specified malloc, there is no reason
926/// to actually DO the malloc. Instead, turn the malloc into a global, and any
927/// loads of GV as uses of the new global.
928static GlobalVariable *
929OptimizeGlobalAddressOfAllocation(GlobalVariable *GV, CallInst *CI,
930 uint64_t AllocSize, Constant *InitVal,
931 const DataLayout &DL,
932 TargetLibraryInfo *TLI) {
933 LLVM_DEBUG(errs() << "PROMOTING GLOBAL: " << *GV << " CALL = " << *CI
934 << '\n');
935
936 // Create global of type [AllocSize x i8].
937 Type *GlobalType = ArrayType::get(ElementType: Type::getInt8Ty(C&: GV->getContext()),
938 NumElements: AllocSize);
939
940 // Create the new global variable. The contents of the allocated memory is
941 // undefined initially, so initialize with an undef value.
942 GlobalVariable *NewGV = new GlobalVariable(
943 *GV->getParent(), GlobalType, false, GlobalValue::InternalLinkage,
944 UndefValue::get(T: GlobalType), GV->getName() + ".body", nullptr,
945 GV->getThreadLocalMode());
946
947 // Initialize the global at the point of the original call. Note that this
948 // is a different point from the initialization referred to below for the
949 // nullability handling. Sublety: We have not proven the original global was
950 // only initialized once. As such, we can not fold this into the initializer
951 // of the new global as may need to re-init the storage multiple times.
952 if (!isa<UndefValue>(Val: InitVal)) {
953 IRBuilder<> Builder(CI->getNextNode());
954 // TODO: Use alignment above if align!=1
955 Builder.CreateMemSet(Ptr: NewGV, Val: InitVal, Size: AllocSize, Align: std::nullopt);
956 }
957
958 // Update users of the allocation to use the new global instead.
959 CI->replaceAllUsesWith(V: NewGV);
960
961 // If there is a comparison against null, we will insert a global bool to
962 // keep track of whether the global was initialized yet or not.
963 GlobalVariable *InitBool = new GlobalVariable(
964 Type::getInt1Ty(C&: GV->getContext()), false, GlobalValue::InternalLinkage,
965 ConstantInt::getFalse(Context&: GV->getContext()), GV->getName() + ".init",
966 GV->getThreadLocalMode(), GV->getAddressSpace());
967 bool InitBoolUsed = false;
968
969 // Loop over all instruction uses of GV, processing them in turn.
970 SmallVector<Value *, 4> Guses;
971 allUsesOfLoadAndStores(GV, Uses&: Guses);
972 for (auto *U : Guses) {
973 if (StoreInst *SI = dyn_cast<StoreInst>(Val: U)) {
974 // The global is initialized when the store to it occurs. If the stored
975 // value is null value, the global bool is set to false, otherwise true.
976 auto *NewSI = new StoreInst(
977 ConstantInt::getBool(Context&: GV->getContext(), V: !isa<ConstantPointerNull>(
978 Val: SI->getValueOperand())),
979 InitBool, false, Align(1), SI->getOrdering(), SI->getSyncScopeID(),
980 SI->getIterator());
981 NewSI->setDebugLoc(SI->getDebugLoc());
982 SI->eraseFromParent();
983 continue;
984 }
985
986 LoadInst *LI = cast<LoadInst>(Val: U);
987 while (!LI->use_empty()) {
988 Use &LoadUse = *LI->use_begin();
989 ICmpInst *ICI = dyn_cast<ICmpInst>(Val: LoadUse.getUser());
990 if (!ICI) {
991 LoadUse.set(NewGV);
992 continue;
993 }
994
995 // Replace the cmp X, 0 with a use of the bool value.
996 Value *LV = new LoadInst(InitBool->getValueType(), InitBool,
997 InitBool->getName() + ".val", false, Align(1),
998 LI->getOrdering(), LI->getSyncScopeID(),
999 LI->getIterator());
1000 // FIXME: Should we use the DebugLoc of the load used by the predicate, or
1001 // the predicate? The load seems most appropriate, but there's an argument
1002 // that the new load does not represent the old load, but is simply a
1003 // component of recomputing the predicate.
1004 cast<LoadInst>(Val: LV)->setDebugLoc(LI->getDebugLoc());
1005 InitBoolUsed = true;
1006 switch (ICI->getPredicate()) {
1007 default: llvm_unreachable("Unknown ICmp Predicate!");
1008 case ICmpInst::ICMP_ULT: // X < null -> always false
1009 LV = ConstantInt::getFalse(Context&: GV->getContext());
1010 break;
1011 case ICmpInst::ICMP_UGE: // X >= null -> always true
1012 LV = ConstantInt::getTrue(Context&: GV->getContext());
1013 break;
1014 case ICmpInst::ICMP_ULE:
1015 case ICmpInst::ICMP_EQ:
1016 LV = BinaryOperator::CreateNot(Op: LV, Name: "notinit", InsertBefore: ICI->getIterator());
1017 cast<BinaryOperator>(Val: LV)->setDebugLoc(ICI->getDebugLoc());
1018 break;
1019 case ICmpInst::ICMP_NE:
1020 case ICmpInst::ICMP_UGT:
1021 break; // no change.
1022 }
1023 ICI->replaceAllUsesWith(V: LV);
1024 ICI->eraseFromParent();
1025 }
1026 LI->eraseFromParent();
1027 }
1028
1029 // If the initialization boolean was used, insert it, otherwise delete it.
1030 if (!InitBoolUsed) {
1031 while (!InitBool->use_empty()) // Delete initializations
1032 cast<StoreInst>(Val: InitBool->user_back())->eraseFromParent();
1033 delete InitBool;
1034 } else
1035 GV->getParent()->insertGlobalVariable(Where: GV->getIterator(), GV: InitBool);
1036
1037 // Now the GV is dead, nuke it and the allocation..
1038 GV->eraseFromParent();
1039 CI->eraseFromParent();
1040
1041 // To further other optimizations, loop over all users of NewGV and try to
1042 // constant prop them. This will promote GEP instructions with constant
1043 // indices into GEP constant-exprs, which will allow global-opt to hack on it.
1044 ConstantPropUsersOf(V: NewGV, DL, TLI);
1045
1046 return NewGV;
1047}
1048
1049/// Scan the use-list of GV checking to make sure that there are no complex uses
1050/// of GV. We permit simple things like dereferencing the pointer, but not
1051/// storing through the address, unless it is to the specified global.
1052static bool
1053valueIsOnlyUsedLocallyOrStoredToOneGlobal(const CallInst *CI,
1054 const GlobalVariable *GV) {
1055 SmallPtrSet<const Value *, 4> Visited;
1056 SmallVector<const Value *, 4> Worklist;
1057 Worklist.push_back(Elt: CI);
1058
1059 while (!Worklist.empty()) {
1060 const Value *V = Worklist.pop_back_val();
1061 if (!Visited.insert(Ptr: V).second)
1062 continue;
1063
1064 for (const Use &VUse : V->uses()) {
1065 const User *U = VUse.getUser();
1066 if (isa<LoadInst>(Val: U) || isa<CmpInst>(Val: U))
1067 continue; // Fine, ignore.
1068
1069 if (auto *SI = dyn_cast<StoreInst>(Val: U)) {
1070 if (SI->getValueOperand() == V &&
1071 SI->getPointerOperand()->stripPointerCasts() != GV)
1072 return false; // Storing the pointer not into GV... bad.
1073 continue; // Otherwise, storing through it, or storing into GV... fine.
1074 }
1075
1076 if (auto *GEPI = dyn_cast<GetElementPtrInst>(Val: U)) {
1077 Worklist.push_back(Elt: GEPI);
1078 continue;
1079 }
1080
1081 return false;
1082 }
1083 }
1084
1085 return true;
1086}
1087
1088/// If we have a global that is only initialized with a fixed size allocation
1089/// try to transform the program to use global memory instead of heap
1090/// allocated memory. This eliminates dynamic allocation, avoids an indirection
1091/// accessing the data, and exposes the resultant global to further GlobalOpt.
1092static bool tryToOptimizeStoreOfAllocationToGlobal(GlobalVariable *GV,
1093 CallInst *CI,
1094 const DataLayout &DL,
1095 TargetLibraryInfo *TLI) {
1096 if (!isRemovableAlloc(V: CI, TLI))
1097 // Must be able to remove the call when we get done..
1098 return false;
1099
1100 Type *Int8Ty = Type::getInt8Ty(C&: CI->getFunction()->getContext());
1101 Constant *InitVal = getInitialValueOfAllocation(V: CI, TLI, Ty: Int8Ty);
1102 if (!InitVal)
1103 // Must be able to emit a memset for initialization
1104 return false;
1105
1106 uint64_t AllocSize;
1107 if (!getObjectSize(Ptr: CI, Size&: AllocSize, DL, TLI, Opts: ObjectSizeOpts()))
1108 return false;
1109
1110 // Restrict this transformation to only working on small allocations
1111 // (2048 bytes currently), as we don't want to introduce a 16M global or
1112 // something.
1113 if (AllocSize >= 2048)
1114 return false;
1115
1116 // We can't optimize this global unless all uses of it are *known* to be
1117 // of the malloc value, not of the null initializer value (consider a use
1118 // that compares the global's value against zero to see if the malloc has
1119 // been reached). To do this, we check to see if all uses of the global
1120 // would trap if the global were null: this proves that they must all
1121 // happen after the malloc.
1122 if (!allUsesOfLoadedValueWillTrapIfNull(GV))
1123 return false;
1124
1125 // We can't optimize this if the malloc itself is used in a complex way,
1126 // for example, being stored into multiple globals. This allows the
1127 // malloc to be stored into the specified global, loaded, gep, icmp'd.
1128 // These are all things we could transform to using the global for.
1129 if (!valueIsOnlyUsedLocallyOrStoredToOneGlobal(CI, GV))
1130 return false;
1131
1132 OptimizeGlobalAddressOfAllocation(GV, CI, AllocSize, InitVal, DL, TLI);
1133 return true;
1134}
1135
1136// Try to optimize globals based on the knowledge that only one value (besides
1137// its initializer) is ever stored to the global.
1138static bool
1139optimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal,
1140 const DataLayout &DL,
1141 function_ref<TargetLibraryInfo &(Function &)> GetTLI) {
1142 // If we are dealing with a pointer global that is initialized to null and
1143 // only has one (non-null) value stored into it, then we can optimize any
1144 // users of the loaded value (often calls and loads) that would trap if the
1145 // value was null.
1146 if (GV->getInitializer()->getType()->isPointerTy() &&
1147 GV->getInitializer()->isNullValue() &&
1148 StoredOnceVal->getType()->isPointerTy() &&
1149 !NullPointerIsDefined(
1150 F: nullptr /* F */,
1151 AS: GV->getInitializer()->getType()->getPointerAddressSpace())) {
1152 if (Constant *SOVC = dyn_cast<Constant>(Val: StoredOnceVal)) {
1153 // Optimize away any trapping uses of the loaded value.
1154 if (OptimizeAwayTrappingUsesOfLoads(GV, LV: SOVC, DL, GetTLI))
1155 return true;
1156 } else if (isAllocationFn(V: StoredOnceVal, GetTLI)) {
1157 if (auto *CI = dyn_cast<CallInst>(Val: StoredOnceVal)) {
1158 auto *TLI = &GetTLI(*CI->getFunction());
1159 if (tryToOptimizeStoreOfAllocationToGlobal(GV, CI, DL, TLI))
1160 return true;
1161 }
1162 }
1163 }
1164
1165 return false;
1166}
1167
1168/// At this point, we have learned that the only two values ever stored into GV
1169/// are its initializer and OtherVal. See if we can shrink the global into a
1170/// boolean and select between the two values whenever it is used. This exposes
1171/// the values to other scalar optimizations.
1172static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) {
1173 Type *GVElType = GV->getValueType();
1174
1175 // If GVElType is already i1, it is already shrunk. If the type of the GV is
1176 // an FP value, pointer or vector, don't do this optimization because a select
1177 // between them is very expensive and unlikely to lead to later
1178 // simplification. In these cases, we typically end up with "cond ? v1 : v2"
1179 // where v1 and v2 both require constant pool loads, a big loss.
1180 if (GVElType == Type::getInt1Ty(C&: GV->getContext()) ||
1181 GVElType->isFloatingPointTy() ||
1182 GVElType->isPointerTy() || GVElType->isVectorTy())
1183 return false;
1184
1185 // Walk the use list of the global seeing if all the uses are load or store.
1186 // If there is anything else, bail out.
1187 for (User *U : GV->users()) {
1188 if (!isa<LoadInst>(Val: U) && !isa<StoreInst>(Val: U))
1189 return false;
1190 if (getLoadStoreType(I: U) != GVElType)
1191 return false;
1192 }
1193
1194 LLVM_DEBUG(dbgs() << " *** SHRINKING TO BOOL: " << *GV << "\n");
1195
1196 // Create the new global, initializing it to false.
1197 GlobalVariable *NewGV = new GlobalVariable(Type::getInt1Ty(C&: GV->getContext()),
1198 false,
1199 GlobalValue::InternalLinkage,
1200 ConstantInt::getFalse(Context&: GV->getContext()),
1201 GV->getName()+".b",
1202 GV->getThreadLocalMode(),
1203 GV->getType()->getAddressSpace());
1204 NewGV->copyAttributesFrom(Src: GV);
1205 GV->getParent()->insertGlobalVariable(Where: GV->getIterator(), GV: NewGV);
1206
1207 Constant *InitVal = GV->getInitializer();
1208 assert(InitVal->getType() != Type::getInt1Ty(GV->getContext()) &&
1209 "No reason to shrink to bool!");
1210
1211 SmallVector<DIGlobalVariableExpression *, 1> GVs;
1212 GV->getDebugInfo(GVs);
1213
1214 // If initialized to zero and storing one into the global, we can use a cast
1215 // instead of a select to synthesize the desired value.
1216 bool IsOneZero = false;
1217 bool EmitOneOrZero = true;
1218 auto *CI = dyn_cast<ConstantInt>(Val: OtherVal);
1219 if (CI && CI->getValue().getActiveBits() <= 64) {
1220 IsOneZero = InitVal->isNullValue() && CI->isOne();
1221
1222 auto *CIInit = dyn_cast<ConstantInt>(Val: GV->getInitializer());
1223 if (CIInit && CIInit->getValue().getActiveBits() <= 64) {
1224 uint64_t ValInit = CIInit->getZExtValue();
1225 uint64_t ValOther = CI->getZExtValue();
1226 uint64_t ValMinus = ValOther - ValInit;
1227
1228 for(auto *GVe : GVs){
1229 DIGlobalVariable *DGV = GVe->getVariable();
1230 DIExpression *E = GVe->getExpression();
1231 const DataLayout &DL = GV->getDataLayout();
1232 unsigned SizeInOctets = NewGV->getGlobalSize(DL);
1233
1234 // It is expected that the address of global optimized variable is on
1235 // top of the stack. After optimization, value of that variable will
1236 // be ether 0 for initial value or 1 for other value. The following
1237 // expression should return constant integer value depending on the
1238 // value at global object address:
1239 // val * (ValOther - ValInit) + ValInit:
1240 // DW_OP_deref DW_OP_constu <ValMinus>
1241 // DW_OP_mul DW_OP_constu <ValInit> DW_OP_plus DW_OP_stack_value
1242 SmallVector<uint64_t, 12> Ops = {
1243 dwarf::DW_OP_deref_size, SizeInOctets,
1244 dwarf::DW_OP_constu, ValMinus,
1245 dwarf::DW_OP_mul, dwarf::DW_OP_constu, ValInit,
1246 dwarf::DW_OP_plus};
1247 bool WithStackValue = true;
1248 E = DIExpression::prependOpcodes(Expr: E, Ops, StackValue: WithStackValue);
1249 DIGlobalVariableExpression *DGVE =
1250 DIGlobalVariableExpression::get(Context&: NewGV->getContext(), Variable: DGV, Expression: E);
1251 NewGV->addDebugInfo(GV: DGVE);
1252 }
1253 EmitOneOrZero = false;
1254 }
1255 }
1256
1257 if (EmitOneOrZero) {
1258 // FIXME: This will only emit address for debugger on which will
1259 // be written only 0 or 1.
1260 for(auto *GV : GVs)
1261 NewGV->addDebugInfo(GV);
1262 }
1263
1264 while (!GV->use_empty()) {
1265 Instruction *UI = cast<Instruction>(Val: GV->user_back());
1266 if (StoreInst *SI = dyn_cast<StoreInst>(Val: UI)) {
1267 // Change the store into a boolean store.
1268 bool StoringOther = SI->getOperand(i_nocapture: 0) == OtherVal;
1269 // Only do this if we weren't storing a loaded value.
1270 Value *StoreVal;
1271 if (StoringOther || SI->getOperand(i_nocapture: 0) == InitVal) {
1272 StoreVal = ConstantInt::get(Ty: Type::getInt1Ty(C&: GV->getContext()),
1273 V: StoringOther);
1274 } else {
1275 // Otherwise, we are storing a previously loaded copy. To do this,
1276 // change the copy from copying the original value to just copying the
1277 // bool.
1278 Instruction *StoredVal = cast<Instruction>(Val: SI->getOperand(i_nocapture: 0));
1279
1280 // If we've already replaced the input, StoredVal will be a cast or
1281 // select instruction. If not, it will be a load of the original
1282 // global.
1283 if (LoadInst *LI = dyn_cast<LoadInst>(Val: StoredVal)) {
1284 assert(LI->getOperand(0) == GV && "Not a copy!");
1285 // Insert a new load, to preserve the saved value.
1286 StoreVal =
1287 new LoadInst(NewGV->getValueType(), NewGV, LI->getName() + ".b",
1288 false, Align(1), LI->getOrdering(),
1289 LI->getSyncScopeID(), LI->getIterator());
1290 cast<LoadInst>(Val: StoreVal)->setDebugLoc(LI->getDebugLoc());
1291 } else {
1292 assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) &&
1293 "This is not a form that we understand!");
1294 StoreVal = StoredVal->getOperand(i: 0);
1295 assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!");
1296 }
1297 }
1298 StoreInst *NSI =
1299 new StoreInst(StoreVal, NewGV, false, Align(1), SI->getOrdering(),
1300 SI->getSyncScopeID(), SI->getIterator());
1301 NSI->setDebugLoc(SI->getDebugLoc());
1302 } else {
1303 // Change the load into a load of bool then a select.
1304 LoadInst *LI = cast<LoadInst>(Val: UI);
1305 LoadInst *NLI = new LoadInst(
1306 NewGV->getValueType(), NewGV, LI->getName() + ".b", false, Align(1),
1307 LI->getOrdering(), LI->getSyncScopeID(), LI->getIterator());
1308 Instruction *NSI;
1309 if (IsOneZero)
1310 NSI = new ZExtInst(NLI, LI->getType(), "", LI->getIterator());
1311 else {
1312 NSI = SelectInst::Create(C: NLI, S1: OtherVal, S2: InitVal, NameStr: "", InsertBefore: LI->getIterator());
1313 setExplicitlyUnknownBranchWeightsIfProfiled(I&: *NSI, DEBUG_TYPE);
1314 }
1315 NSI->takeName(V: LI);
1316 // Since LI is split into two instructions, NLI and NSI both inherit the
1317 // same DebugLoc
1318 NLI->setDebugLoc(LI->getDebugLoc());
1319 NSI->setDebugLoc(LI->getDebugLoc());
1320 LI->replaceAllUsesWith(V: NSI);
1321 }
1322 UI->eraseFromParent();
1323 }
1324
1325 // Retain the name of the old global variable. People who are debugging their
1326 // programs may expect these variables to be named the same.
1327 NewGV->takeName(V: GV);
1328 GV->eraseFromParent();
1329 return true;
1330}
1331
1332static bool
1333deleteIfDead(GlobalValue &GV,
1334 SmallPtrSetImpl<const Comdat *> &NotDiscardableComdats,
1335 function_ref<void(Function &)> DeleteFnCallback = nullptr) {
1336 GV.removeDeadConstantUsers();
1337
1338 if (!GV.isDiscardableIfUnused() && !GV.isDeclaration())
1339 return false;
1340
1341 if (const Comdat *C = GV.getComdat())
1342 if (!GV.hasLocalLinkage() && NotDiscardableComdats.count(Ptr: C))
1343 return false;
1344
1345 bool Dead;
1346 if (auto *F = dyn_cast<Function>(Val: &GV))
1347 Dead = (F->isDeclaration() && F->use_empty()) || F->isDefTriviallyDead();
1348 else
1349 Dead = GV.use_empty();
1350 if (!Dead)
1351 return false;
1352
1353 LLVM_DEBUG(dbgs() << "GLOBAL DEAD: " << GV << "\n");
1354 if (auto *F = dyn_cast<Function>(Val: &GV)) {
1355 if (DeleteFnCallback)
1356 DeleteFnCallback(*F);
1357 }
1358 ReplaceableMetadataImpl::SalvageDebugInfo(C: GV);
1359 GV.eraseFromParent();
1360 ++NumDeleted;
1361 return true;
1362}
1363
1364static bool isPointerValueDeadOnEntryToFunction(
1365 const Function *F, GlobalValue *GV,
1366 function_ref<DominatorTree &(Function &)> LookupDomTree) {
1367 // Find all uses of GV. We expect them all to be in F, and if we can't
1368 // identify any of the uses we bail out.
1369 //
1370 // On each of these uses, identify if the memory that GV points to is
1371 // used/required/live at the start of the function. If it is not, for example
1372 // if the first thing the function does is store to the GV, the GV can
1373 // possibly be demoted.
1374 //
1375 // We don't do an exhaustive search for memory operations - simply look
1376 // through bitcasts as they're quite common and benign.
1377 const DataLayout &DL = GV->getDataLayout();
1378 SmallVector<LoadInst *, 4> Loads;
1379 SmallVector<StoreInst *, 4> Stores;
1380 for (auto *U : GV->users()) {
1381 Instruction *I = dyn_cast<Instruction>(Val: U);
1382 if (!I)
1383 return false;
1384 assert(I->getParent()->getParent() == F);
1385
1386 if (auto *LI = dyn_cast<LoadInst>(Val: I))
1387 Loads.push_back(Elt: LI);
1388 else if (auto *SI = dyn_cast<StoreInst>(Val: I))
1389 Stores.push_back(Elt: SI);
1390 else
1391 return false;
1392 }
1393
1394 // We have identified all uses of GV into loads and stores. Now check if all
1395 // of them are known not to depend on the value of the global at the function
1396 // entry point. We do this by ensuring that every load is dominated by at
1397 // least one store.
1398 auto &DT = LookupDomTree(*const_cast<Function *>(F));
1399
1400 // The below check is quadratic. Check we're not going to do too many tests.
1401 // FIXME: Even though this will always have worst-case quadratic time, we
1402 // could put effort into minimizing the average time by putting stores that
1403 // have been shown to dominate at least one load at the beginning of the
1404 // Stores array, making subsequent dominance checks more likely to succeed
1405 // early.
1406 //
1407 // The threshold here is fairly large because global->local demotion is a
1408 // very powerful optimization should it fire.
1409 const unsigned Threshold = 100;
1410 if (Loads.size() * Stores.size() > Threshold)
1411 return false;
1412
1413 for (auto *L : Loads) {
1414 auto *LTy = L->getType();
1415 if (none_of(Range&: Stores, P: [&](const StoreInst *S) {
1416 auto *STy = S->getValueOperand()->getType();
1417 // The load is only dominated by the store if DomTree says so
1418 // and the number of bits loaded in L is less than or equal to
1419 // the number of bits stored in S.
1420 return DT.dominates(Def: S, User: L) &&
1421 DL.getTypeStoreSize(Ty: LTy).getFixedValue() <=
1422 DL.getTypeStoreSize(Ty: STy).getFixedValue();
1423 }))
1424 return false;
1425 }
1426 // All loads have known dependences inside F, so the global can be localized.
1427 return true;
1428}
1429
1430// For a global variable with one store, if the store dominates any loads,
1431// those loads will always load the stored value (as opposed to the
1432// initializer), even in the presence of recursion.
1433static bool forwardStoredOnceStore(
1434 GlobalVariable *GV, const StoreInst *StoredOnceStore,
1435 function_ref<DominatorTree &(Function &)> LookupDomTree) {
1436 const Value *StoredOnceValue = StoredOnceStore->getValueOperand();
1437 // We can do this optimization for non-constants in nosync + norecurse
1438 // functions, but globals used in exactly one norecurse functions are already
1439 // promoted to an alloca.
1440 if (!isa<Constant>(Val: StoredOnceValue))
1441 return false;
1442 const Function *F = StoredOnceStore->getFunction();
1443 SmallVector<LoadInst *> Loads;
1444 for (User *U : GV->users()) {
1445 if (auto *LI = dyn_cast<LoadInst>(Val: U)) {
1446 if (LI->getFunction() == F &&
1447 LI->getType() == StoredOnceValue->getType() && LI->isSimple())
1448 Loads.push_back(Elt: LI);
1449 }
1450 }
1451 // Only compute DT if we have any loads to examine.
1452 bool MadeChange = false;
1453 if (!Loads.empty()) {
1454 auto &DT = LookupDomTree(*const_cast<Function *>(F));
1455 for (auto *LI : Loads) {
1456 if (DT.dominates(Def: StoredOnceStore, User: LI)) {
1457 LI->replaceAllUsesWith(V: const_cast<Value *>(StoredOnceValue));
1458 LI->eraseFromParent();
1459 MadeChange = true;
1460 }
1461 }
1462 }
1463 return MadeChange;
1464}
1465
1466/// Analyze the specified global variable and optimize
1467/// it if possible. If we make a change, return true.
1468static bool
1469processInternalGlobal(GlobalVariable *GV, const GlobalStatus &GS,
1470 function_ref<TargetTransformInfo &(Function &)> GetTTI,
1471 function_ref<TargetLibraryInfo &(Function &)> GetTLI,
1472 function_ref<DominatorTree &(Function &)> LookupDomTree) {
1473 auto &DL = GV->getDataLayout();
1474 // If this is a first class global and has only one accessing function and
1475 // this function is non-recursive, we replace the global with a local alloca
1476 // in this function.
1477 //
1478 // NOTE: It doesn't make sense to promote non-single-value types since we
1479 // are just replacing static memory to stack memory.
1480 //
1481 // If the global is in different address space, don't bring it to stack.
1482 if (!GS.HasMultipleAccessingFunctions &&
1483 GS.AccessingFunction &&
1484 GV->getValueType()->isSingleValueType() &&
1485 GV->getType()->getAddressSpace() == DL.getAllocaAddrSpace() &&
1486 !GV->isExternallyInitialized() &&
1487 GS.AccessingFunction->doesNotRecurse() &&
1488 isPointerValueDeadOnEntryToFunction(F: GS.AccessingFunction, GV,
1489 LookupDomTree)) {
1490 const DataLayout &DL = GV->getDataLayout();
1491
1492 LLVM_DEBUG(dbgs() << "LOCALIZING GLOBAL: " << *GV << "\n");
1493 BasicBlock::iterator FirstI =
1494 GS.AccessingFunction->getEntryBlock().begin().getNonConst();
1495 Type *ElemTy = GV->getValueType();
1496 // FIXME: Pass Global's alignment when globals have alignment
1497 AllocaInst *Alloca = new AllocaInst(ElemTy, DL.getAllocaAddrSpace(),
1498 nullptr, GV->getName(), FirstI);
1499 Alloca->setDebugLoc(DebugLoc::getCompilerGenerated());
1500 if (!isa<UndefValue>(Val: GV->getInitializer())) {
1501 auto *SI = new StoreInst(GV->getInitializer(), Alloca, FirstI);
1502 // FIXME: We're localizing a global and creating a store instruction for
1503 // the initial value of that global. Could we logically use the global
1504 // variable's (if one exists) line for this?
1505 SI->setDebugLoc(DebugLoc::getCompilerGenerated());
1506 }
1507
1508 GV->replaceAllUsesWith(V: Alloca);
1509 GV->eraseFromParent();
1510 ++NumLocalized;
1511 return true;
1512 }
1513
1514 bool Changed = false;
1515
1516 // If the global is never loaded (but may be stored to), it is dead.
1517 // Delete it now.
1518 if (!GS.IsLoaded) {
1519 LLVM_DEBUG(dbgs() << "GLOBAL NEVER LOADED: " << *GV << "\n");
1520
1521 if (isLeakCheckerRoot(GV)) {
1522 // Delete any constant stores to the global.
1523 Changed = CleanupPointerRootUsers(GV, GetTLI);
1524 } else {
1525 // Delete any stores we can find to the global. We may not be able to
1526 // make it completely dead though.
1527 Changed = CleanupConstantGlobalUsers(GV, DL);
1528 }
1529
1530 // If the global is dead now, delete it.
1531 if (GV->use_empty()) {
1532 GV->eraseFromParent();
1533 ++NumDeleted;
1534 Changed = true;
1535 }
1536 return Changed;
1537
1538 }
1539 if (GS.StoredType <= GlobalStatus::InitializerStored) {
1540 LLVM_DEBUG(dbgs() << "MARKING CONSTANT: " << *GV << "\n");
1541
1542 // Don't actually mark a global constant if it's atomic because atomic loads
1543 // are implemented by a trivial cmpxchg in some edge-cases and that usually
1544 // requires write access to the variable even if it's not actually changed.
1545 if (GS.Ordering == AtomicOrdering::NotAtomic) {
1546 assert(!GV->isConstant() && "Expected a non-constant global");
1547 GV->setConstant(true);
1548 Changed = true;
1549 }
1550
1551 // Clean up any obviously simplifiable users now.
1552 Changed |= CleanupConstantGlobalUsers(GV, DL);
1553
1554 // If the global is dead now, just nuke it.
1555 if (GV->use_empty()) {
1556 LLVM_DEBUG(dbgs() << " *** Marking constant allowed us to simplify "
1557 << "all users and delete global!\n");
1558 GV->eraseFromParent();
1559 ++NumDeleted;
1560 return true;
1561 }
1562
1563 // Fall through to the next check; see if we can optimize further.
1564 ++NumMarked;
1565 }
1566 if (!GV->getInitializer()->getType()->isSingleValueType()) {
1567 const DataLayout &DL = GV->getDataLayout();
1568 if (SRAGlobal(GV, DL))
1569 return true;
1570 }
1571 Value *StoredOnceValue = GS.getStoredOnceValue();
1572 if (GS.StoredType == GlobalStatus::StoredOnce && StoredOnceValue) {
1573 Function &StoreFn =
1574 const_cast<Function &>(*GS.StoredOnceStore->getFunction());
1575 bool CanHaveNonUndefGlobalInitializer =
1576 GetTTI(StoreFn).canHaveNonUndefGlobalInitializerInAddressSpace(
1577 AS: GV->getType()->getAddressSpace());
1578 // If the initial value for the global was an undef value, and if only
1579 // one other value was stored into it, we can just change the
1580 // initializer to be the stored value, then delete all stores to the
1581 // global. This allows us to mark it constant.
1582 // This is restricted to address spaces that allow globals to have
1583 // initializers. NVPTX, for example, does not support initializers for
1584 // shared memory (AS 3).
1585 auto *SOVConstant = dyn_cast<Constant>(Val: StoredOnceValue);
1586 if (SOVConstant && isa<UndefValue>(Val: GV->getInitializer()) &&
1587 DL.getTypeAllocSize(Ty: SOVConstant->getType()).getFixedValue() ==
1588 GV->getGlobalSize(DL) &&
1589 CanHaveNonUndefGlobalInitializer) {
1590 if (SOVConstant->getType() == GV->getValueType()) {
1591 // Change the initializer in place.
1592 GV->setInitializer(SOVConstant);
1593 } else {
1594 // Create a new global with adjusted type.
1595 auto *NGV = new GlobalVariable(
1596 *GV->getParent(), SOVConstant->getType(), GV->isConstant(),
1597 GV->getLinkage(), SOVConstant, "", GV, GV->getThreadLocalMode(),
1598 GV->getAddressSpace());
1599 NGV->takeName(V: GV);
1600 NGV->copyAttributesFrom(Src: GV);
1601 GV->replaceAllUsesWith(V: NGV);
1602 GV->eraseFromParent();
1603 GV = NGV;
1604 }
1605
1606 // Clean up any obviously simplifiable users now.
1607 CleanupConstantGlobalUsers(GV, DL);
1608
1609 if (GV->use_empty()) {
1610 LLVM_DEBUG(dbgs() << " *** Substituting initializer allowed us to "
1611 << "simplify all users and delete global!\n");
1612 GV->eraseFromParent();
1613 ++NumDeleted;
1614 }
1615 ++NumSubstitute;
1616 return true;
1617 }
1618
1619 // Try to optimize globals based on the knowledge that only one value
1620 // (besides its initializer) is ever stored to the global.
1621 if (optimizeOnceStoredGlobal(GV, StoredOnceVal: StoredOnceValue, DL, GetTLI))
1622 return true;
1623
1624 // Try to forward the store to any loads. If we have more than one store, we
1625 // may have a store of the initializer between StoredOnceStore and a load.
1626 if (GS.NumStores == 1)
1627 if (forwardStoredOnceStore(GV, StoredOnceStore: GS.StoredOnceStore, LookupDomTree))
1628 return true;
1629
1630 // Otherwise, if the global was not a boolean, we can shrink it to be a
1631 // boolean. Skip this optimization for AS that doesn't allow an initializer.
1632 if (SOVConstant && GS.Ordering == AtomicOrdering::NotAtomic &&
1633 (!isa<UndefValue>(Val: GV->getInitializer()) ||
1634 CanHaveNonUndefGlobalInitializer)) {
1635 if (TryToShrinkGlobalToBoolean(GV, OtherVal: SOVConstant)) {
1636 ++NumShrunkToBool;
1637 return true;
1638 }
1639 }
1640 }
1641
1642 return Changed;
1643}
1644
1645/// Analyze the specified global variable and optimize it if possible. If we
1646/// make a change, return true.
1647static bool
1648processGlobal(GlobalValue &GV,
1649 function_ref<TargetTransformInfo &(Function &)> GetTTI,
1650 function_ref<TargetLibraryInfo &(Function &)> GetTLI,
1651 function_ref<DominatorTree &(Function &)> LookupDomTree) {
1652 if (GV.getName().starts_with(Prefix: "llvm."))
1653 return false;
1654
1655 GlobalStatus GS;
1656
1657 if (GlobalStatus::analyzeGlobal(V: &GV, GS))
1658 return false;
1659
1660 bool Changed = false;
1661 if (!GS.IsCompared && !GV.hasGlobalUnnamedAddr()) {
1662 auto NewUnnamedAddr = GV.hasLocalLinkage() ? GlobalValue::UnnamedAddr::Global
1663 : GlobalValue::UnnamedAddr::Local;
1664 if (NewUnnamedAddr != GV.getUnnamedAddr()) {
1665 GV.setUnnamedAddr(NewUnnamedAddr);
1666 NumUnnamed++;
1667 Changed = true;
1668 }
1669 }
1670
1671 // Do more involved optimizations if the global is internal.
1672 if (!GV.hasLocalLinkage())
1673 return Changed;
1674
1675 auto *GVar = dyn_cast<GlobalVariable>(Val: &GV);
1676 if (!GVar)
1677 return Changed;
1678
1679 if (GVar->isConstant() || !GVar->hasInitializer())
1680 return Changed;
1681
1682 return processInternalGlobal(GV: GVar, GS, GetTTI, GetTLI, LookupDomTree) ||
1683 Changed;
1684}
1685
1686/// Walk all of the direct calls of the specified function, changing them to
1687/// FastCC.
1688static void ChangeCalleesToFastCall(Function *F) {
1689 for (User *U : F->users())
1690 if (auto *Call = dyn_cast<CallBase>(Val: U))
1691 if (Call->getCalledOperand() == F)
1692 Call->setCallingConv(CallingConv::Fast);
1693}
1694
1695static AttributeList StripAttr(LLVMContext &C, AttributeList Attrs,
1696 Attribute::AttrKind A) {
1697 unsigned AttrIndex;
1698 if (Attrs.hasAttrSomewhere(Kind: A, Index: &AttrIndex))
1699 return Attrs.removeAttributeAtIndex(C, Index: AttrIndex, Kind: A);
1700 return Attrs;
1701}
1702
1703static void RemoveAttribute(Function *F, Attribute::AttrKind A) {
1704 F->setAttributes(StripAttr(C&: F->getContext(), Attrs: F->getAttributes(), A));
1705 for (User *U : F->users()) {
1706 CallBase *CB = cast<CallBase>(Val: U);
1707 CB->setAttributes(StripAttr(C&: F->getContext(), Attrs: CB->getAttributes(), A));
1708 }
1709}
1710
1711/// Return true if this is a calling convention that we'd like to change. The
1712/// idea here is that we don't want to mess with the convention if the user
1713/// explicitly requested something with performance implications like coldcc,
1714/// GHC, or anyregcc.
1715static bool hasChangeableCCImpl(Function *F) {
1716 CallingConv::ID CC = F->getCallingConv();
1717
1718 // FIXME: Is it worth transforming x86_stdcallcc and x86_fastcallcc?
1719 if (CC != CallingConv::C && CC != CallingConv::X86_ThisCall)
1720 return false;
1721
1722 if (F->isVarArg())
1723 return false;
1724
1725 // FIXME: Change CC for the whole chain of musttail calls when possible.
1726 //
1727 // Can't change CC of the function that either has musttail calls, or is a
1728 // musttail callee itself
1729 for (User *U : F->users()) {
1730 CallInst* CI = dyn_cast<CallInst>(Val: U);
1731 if (!CI)
1732 continue;
1733
1734 if (CI->isMustTailCall())
1735 return false;
1736 }
1737
1738 for (BasicBlock &BB : *F)
1739 if (BB.getTerminatingMustTailCall())
1740 return false;
1741
1742 return !F->hasAddressTaken();
1743}
1744
1745using ChangeableCCCacheTy = SmallDenseMap<Function *, bool, 8>;
1746static bool hasChangeableCC(Function *F,
1747 ChangeableCCCacheTy &ChangeableCCCache) {
1748 auto Res = ChangeableCCCache.try_emplace(Key: F, Args: false);
1749 if (Res.second)
1750 Res.first->second = hasChangeableCCImpl(F);
1751 return Res.first->second;
1752}
1753
1754/// Return true if the block containing the call site has a BlockFrequency of
1755/// less than ColdCCRelFreq% of the entry block.
1756static bool isColdCallSite(CallBase &CB, BlockFrequencyInfo &CallerBFI) {
1757 const BranchProbability ColdProb(ColdCCRelFreq, 100);
1758 auto *CallSiteBB = CB.getParent();
1759 auto CallSiteFreq = CallerBFI.getBlockFreq(BB: CallSiteBB);
1760 auto CallerEntryFreq =
1761 CallerBFI.getBlockFreq(BB: &(CB.getCaller()->getEntryBlock()));
1762 return CallSiteFreq < CallerEntryFreq * ColdProb;
1763}
1764
1765// This function checks if the input function F is cold at all call sites. It
1766// also looks each call site's containing function, returning false if the
1767// caller function contains other non cold calls. The input vector AllCallsCold
1768// contains a list of functions that only have call sites in cold blocks.
1769static bool
1770isValidCandidateForColdCC(Function &F,
1771 function_ref<BlockFrequencyInfo &(Function &)> GetBFI,
1772 const std::vector<Function *> &AllCallsCold) {
1773
1774 if (F.user_empty())
1775 return false;
1776
1777 for (User *U : F.users()) {
1778 CallBase *CB = dyn_cast<CallBase>(Val: U);
1779 if (!CB || CB->getCalledOperand() != &F)
1780 continue;
1781 Function *CallerFunc = CB->getParent()->getParent();
1782 BlockFrequencyInfo &CallerBFI = GetBFI(*CallerFunc);
1783 if (!isColdCallSite(CB&: *CB, CallerBFI))
1784 return false;
1785 if (!llvm::is_contained(Range: AllCallsCold, Element: CallerFunc))
1786 return false;
1787 }
1788 return true;
1789}
1790
1791static void changeCallSitesToColdCC(Function *F) {
1792 for (User *U : F->users())
1793 if (auto *Call = dyn_cast<CallBase>(Val: U))
1794 if (Call->getCalledOperand() == F)
1795 Call->setCallingConv(CallingConv::Cold);
1796}
1797
1798// This function iterates over all the call instructions in the input Function
1799// and checks that all call sites are in cold blocks and are allowed to use the
1800// coldcc calling convention.
1801static bool
1802hasOnlyColdCalls(Function &F,
1803 function_ref<BlockFrequencyInfo &(Function &)> GetBFI,
1804 ChangeableCCCacheTy &ChangeableCCCache) {
1805 for (BasicBlock &BB : F) {
1806 for (Instruction &I : BB) {
1807 if (CallInst *CI = dyn_cast<CallInst>(Val: &I)) {
1808 // Skip over isline asm instructions since they aren't function calls.
1809 if (CI->isInlineAsm())
1810 continue;
1811 Function *CalledFn = CI->getCalledFunction();
1812 if (!CalledFn)
1813 return false;
1814 // Skip over intrinsics since they won't remain as function calls.
1815 // Important to do this check before the linkage check below so we
1816 // won't bail out on debug intrinsics, possibly making the generated
1817 // code dependent on the presence of debug info.
1818 if (CalledFn->getIntrinsicID() != Intrinsic::not_intrinsic)
1819 continue;
1820 if (!CalledFn->hasLocalLinkage())
1821 return false;
1822 // Check if it's valid to use coldcc calling convention.
1823 if (!hasChangeableCC(F: CalledFn, ChangeableCCCache))
1824 return false;
1825 BlockFrequencyInfo &CallerBFI = GetBFI(F);
1826 if (!isColdCallSite(CB&: *CI, CallerBFI))
1827 return false;
1828 }
1829 }
1830 }
1831 return true;
1832}
1833
1834static bool hasMustTailCallers(Function *F) {
1835 for (User *U : F->users()) {
1836 CallBase *CB = cast<CallBase>(Val: U);
1837 if (CB->isMustTailCall())
1838 return true;
1839 }
1840 return false;
1841}
1842
1843static bool hasInvokeCallers(Function *F) {
1844 for (User *U : F->users())
1845 if (isa<InvokeInst>(Val: U))
1846 return true;
1847 return false;
1848}
1849
1850static void RemovePreallocated(Function *F) {
1851 RemoveAttribute(F, A: Attribute::Preallocated);
1852
1853 auto *M = F->getParent();
1854
1855 IRBuilder<> Builder(M->getContext());
1856
1857 // Cannot modify users() while iterating over it, so make a copy.
1858 SmallVector<User *, 4> PreallocatedCalls(F->users());
1859 for (User *U : PreallocatedCalls) {
1860 CallBase *CB = dyn_cast<CallBase>(Val: U);
1861 if (!CB)
1862 continue;
1863
1864 assert(
1865 !CB->isMustTailCall() &&
1866 "Shouldn't call RemotePreallocated() on a musttail preallocated call");
1867 // Create copy of call without "preallocated" operand bundle.
1868 SmallVector<OperandBundleDef, 1> OpBundles;
1869 CB->getOperandBundlesAsDefs(Defs&: OpBundles);
1870 CallBase *PreallocatedSetup = nullptr;
1871 for (auto *It = OpBundles.begin(); It != OpBundles.end(); ++It) {
1872 if (It->getTag() == "preallocated") {
1873 PreallocatedSetup = cast<CallBase>(Val: *It->input_begin());
1874 OpBundles.erase(CI: It);
1875 break;
1876 }
1877 }
1878 assert(PreallocatedSetup && "Did not find preallocated bundle");
1879 uint64_t ArgCount =
1880 cast<ConstantInt>(Val: PreallocatedSetup->getArgOperand(i: 0))->getZExtValue();
1881
1882 assert((isa<CallInst>(CB) || isa<InvokeInst>(CB)) &&
1883 "Unknown indirect call type");
1884 CallBase *NewCB = CallBase::Create(CB, Bundles: OpBundles, InsertPt: CB->getIterator());
1885 CB->replaceAllUsesWith(V: NewCB);
1886 NewCB->takeName(V: CB);
1887 CB->eraseFromParent();
1888
1889 Builder.SetInsertPoint(PreallocatedSetup);
1890 auto *StackSave = Builder.CreateStackSave();
1891 Builder.SetInsertPoint(NewCB->getNextNode());
1892 Builder.CreateStackRestore(Ptr: StackSave);
1893
1894 // Replace @llvm.call.preallocated.arg() with alloca.
1895 // Cannot modify users() while iterating over it, so make a copy.
1896 // @llvm.call.preallocated.arg() can be called with the same index multiple
1897 // times. So for each @llvm.call.preallocated.arg(), we see if we have
1898 // already created a Value* for the index, and if not, create an alloca and
1899 // bitcast right after the @llvm.call.preallocated.setup() so that it
1900 // dominates all uses.
1901 SmallVector<Value *, 2> ArgAllocas(ArgCount);
1902 SmallVector<User *, 2> PreallocatedArgs(PreallocatedSetup->users());
1903 for (auto *User : PreallocatedArgs) {
1904 auto *UseCall = cast<CallBase>(Val: User);
1905 assert(UseCall->getCalledFunction()->getIntrinsicID() ==
1906 Intrinsic::call_preallocated_arg &&
1907 "preallocated token use was not a llvm.call.preallocated.arg");
1908 uint64_t AllocArgIndex =
1909 cast<ConstantInt>(Val: UseCall->getArgOperand(i: 1))->getZExtValue();
1910 Value *AllocaReplacement = ArgAllocas[AllocArgIndex];
1911 if (!AllocaReplacement) {
1912 auto AddressSpace = UseCall->getType()->getPointerAddressSpace();
1913 auto *ArgType =
1914 UseCall->getFnAttr(Kind: Attribute::Preallocated).getValueAsType();
1915 auto *InsertBefore = PreallocatedSetup->getNextNode();
1916 Builder.SetInsertPoint(InsertBefore);
1917 auto *Alloca =
1918 Builder.CreateAlloca(Ty: ArgType, AddrSpace: AddressSpace, ArraySize: nullptr, Name: "paarg");
1919 ArgAllocas[AllocArgIndex] = Alloca;
1920 AllocaReplacement = Alloca;
1921 }
1922
1923 UseCall->replaceAllUsesWith(V: AllocaReplacement);
1924 UseCall->eraseFromParent();
1925 }
1926 // Remove @llvm.call.preallocated.setup().
1927 cast<Instruction>(Val: PreallocatedSetup)->eraseFromParent();
1928 }
1929}
1930
1931static bool
1932OptimizeFunctions(Module &M,
1933 function_ref<TargetLibraryInfo &(Function &)> GetTLI,
1934 function_ref<TargetTransformInfo &(Function &)> GetTTI,
1935 function_ref<BlockFrequencyInfo &(Function &)> GetBFI,
1936 function_ref<DominatorTree &(Function &)> LookupDomTree,
1937 SmallPtrSetImpl<const Comdat *> &NotDiscardableComdats,
1938 function_ref<void(Function &F)> ChangedCFGCallback,
1939 function_ref<void(Function &F)> DeleteFnCallback) {
1940
1941 bool Changed = false;
1942
1943 ChangeableCCCacheTy ChangeableCCCache;
1944 std::vector<Function *> AllCallsCold;
1945 for (Function &F : llvm::make_early_inc_range(Range&: M))
1946 if (hasOnlyColdCalls(F, GetBFI, ChangeableCCCache))
1947 AllCallsCold.push_back(x: &F);
1948
1949 // Optimize functions.
1950 for (Function &F : llvm::make_early_inc_range(Range&: M)) {
1951 // Don't perform global opt pass on naked functions; we don't want fast
1952 // calling conventions for naked functions.
1953 if (F.hasFnAttribute(Kind: Attribute::Naked))
1954 continue;
1955
1956 // Functions without names cannot be referenced outside this module.
1957 if (!F.hasName() && !F.isDeclaration() && !F.hasLocalLinkage())
1958 F.setLinkage(GlobalValue::InternalLinkage);
1959
1960 if (deleteIfDead(GV&: F, NotDiscardableComdats, DeleteFnCallback)) {
1961 Changed = true;
1962 continue;
1963 }
1964
1965 // LLVM's definition of dominance allows instructions that are cyclic
1966 // in unreachable blocks, e.g.:
1967 // %pat = select i1 %condition, @global, i16* %pat
1968 // because any instruction dominates an instruction in a block that's
1969 // not reachable from entry.
1970 // So, remove unreachable blocks from the function, because a) there's
1971 // no point in analyzing them and b) GlobalOpt should otherwise grow
1972 // some more complicated logic to break these cycles.
1973 // Notify the analysis manager that we've modified the function's CFG.
1974 if (!F.isDeclaration()) {
1975 if (removeUnreachableBlocks(F)) {
1976 Changed = true;
1977 ChangedCFGCallback(F);
1978 }
1979 }
1980
1981 Changed |= processGlobal(GV&: F, GetTTI, GetTLI, LookupDomTree);
1982
1983 if (!F.hasLocalLinkage())
1984 continue;
1985
1986 // If we have an inalloca parameter that we can safely remove the
1987 // inalloca attribute from, do so. This unlocks optimizations that
1988 // wouldn't be safe in the presence of inalloca.
1989 // FIXME: We should also hoist alloca affected by this to the entry
1990 // block if possible.
1991 if (F.getAttributes().hasAttrSomewhere(Kind: Attribute::InAlloca) &&
1992 !F.hasAddressTaken() && !hasMustTailCallers(F: &F) && !F.isVarArg()) {
1993 RemoveAttribute(F: &F, A: Attribute::InAlloca);
1994 Changed = true;
1995 }
1996
1997 // FIXME: handle invokes
1998 // FIXME: handle musttail
1999 if (F.getAttributes().hasAttrSomewhere(Kind: Attribute::Preallocated)) {
2000 if (!F.hasAddressTaken() && !hasMustTailCallers(F: &F) &&
2001 !hasInvokeCallers(F: &F)) {
2002 RemovePreallocated(F: &F);
2003 Changed = true;
2004 }
2005 continue;
2006 }
2007
2008 if (hasChangeableCC(F: &F, ChangeableCCCache)) {
2009 NumInternalFunc++;
2010 TargetTransformInfo &TTI = GetTTI(F);
2011 // Change the calling convention to coldcc if either stress testing is
2012 // enabled or the target would like to use coldcc on functions which are
2013 // cold at all call sites and the callers contain no other non coldcc
2014 // calls.
2015 if (EnableColdCCStressTest ||
2016 (TTI.useColdCCForColdCall(F) &&
2017 isValidCandidateForColdCC(F, GetBFI, AllCallsCold))) {
2018 ChangeableCCCache.erase(Val: &F);
2019 F.setCallingConv(CallingConv::Cold);
2020 changeCallSitesToColdCC(F: &F);
2021 Changed = true;
2022 NumColdCC++;
2023 }
2024 }
2025
2026 if (hasChangeableCC(F: &F, ChangeableCCCache)) {
2027 // If this function has a calling convention worth changing, is not a
2028 // varargs function, is only called directly, and is supported by the
2029 // target, promote it to use the Fast calling convention.
2030 TargetTransformInfo &TTI = GetTTI(F);
2031 if (TTI.useFastCCForInternalCall(F)) {
2032 F.setCallingConv(CallingConv::Fast);
2033 ChangeCalleesToFastCall(F: &F);
2034 ++NumFastCallFns;
2035 Changed = true;
2036 }
2037 }
2038
2039 if (F.getAttributes().hasAttrSomewhere(Kind: Attribute::Nest) &&
2040 !F.hasAddressTaken()) {
2041 // The function is not used by a trampoline intrinsic, so it is safe
2042 // to remove the 'nest' attribute.
2043 RemoveAttribute(F: &F, A: Attribute::Nest);
2044 ++NumNestRemoved;
2045 Changed = true;
2046 }
2047 }
2048 return Changed;
2049}
2050
2051static bool
2052OptimizeGlobalVars(Module &M,
2053 function_ref<TargetTransformInfo &(Function &)> GetTTI,
2054 function_ref<TargetLibraryInfo &(Function &)> GetTLI,
2055 function_ref<DominatorTree &(Function &)> LookupDomTree,
2056 SmallPtrSetImpl<const Comdat *> &NotDiscardableComdats) {
2057 bool Changed = false;
2058
2059 for (GlobalVariable &GV : llvm::make_early_inc_range(Range: M.globals())) {
2060 // Global variables without names cannot be referenced outside this module.
2061 if (!GV.hasName() && !GV.isDeclaration() && !GV.hasLocalLinkage())
2062 GV.setLinkage(GlobalValue::InternalLinkage);
2063 // Simplify the initializer.
2064 if (GV.hasInitializer())
2065 if (auto *C = dyn_cast<Constant>(Val: GV.getInitializer())) {
2066 auto &DL = M.getDataLayout();
2067 // TLI is not used in the case of a Constant, so use default nullptr
2068 // for that optional parameter, since we don't have a Function to
2069 // provide GetTLI anyway.
2070 Constant *New = ConstantFoldConstant(C, DL, /*TLI*/ nullptr);
2071 if (New != C)
2072 GV.setInitializer(New);
2073 }
2074
2075 if (deleteIfDead(GV, NotDiscardableComdats)) {
2076 Changed = true;
2077 continue;
2078 }
2079
2080 Changed |= processGlobal(GV, GetTTI, GetTLI, LookupDomTree);
2081 }
2082 return Changed;
2083}
2084
2085/// Evaluate static constructors in the function, if we can. Return true if we
2086/// can, false otherwise.
2087static bool EvaluateStaticConstructor(Function *F, const DataLayout &DL,
2088 TargetLibraryInfo *TLI) {
2089 // Skip external functions.
2090 if (F->isDeclaration())
2091 return false;
2092 // Call the function.
2093 Evaluator Eval(DL, TLI);
2094 Constant *RetValDummy;
2095 bool EvalSuccess = Eval.EvaluateFunction(F, RetVal&: RetValDummy,
2096 ActualArgs: SmallVector<Constant*, 0>());
2097
2098 if (EvalSuccess) {
2099 ++NumCtorsEvaluated;
2100
2101 // We succeeded at evaluation: commit the result.
2102 auto NewInitializers = Eval.getMutatedInitializers();
2103 LLVM_DEBUG(dbgs() << "FULLY EVALUATED GLOBAL CTOR FUNCTION '"
2104 << F->getName() << "' to " << NewInitializers.size()
2105 << " stores.\n");
2106 for (const auto &Pair : NewInitializers)
2107 Pair.first->setInitializer(Pair.second);
2108 for (GlobalVariable *GV : Eval.getInvariants())
2109 GV->setConstant(true);
2110 }
2111
2112 return EvalSuccess;
2113}
2114
2115static int compareNames(Constant *const *A, Constant *const *B) {
2116 Value *AStripped = (*A)->stripPointerCasts();
2117 Value *BStripped = (*B)->stripPointerCasts();
2118 return AStripped->getName().compare(RHS: BStripped->getName());
2119}
2120
2121static void setUsedInitializer(GlobalVariable &V,
2122 const SmallPtrSetImpl<GlobalValue *> &Init) {
2123 if (Init.empty()) {
2124 V.eraseFromParent();
2125 return;
2126 }
2127
2128 // Get address space of pointers in the array of pointers.
2129 const Type *UsedArrayType = V.getValueType();
2130 const auto *VAT = cast<ArrayType>(Val: UsedArrayType);
2131 const auto *VEPT = cast<PointerType>(Val: VAT->getArrayElementType());
2132
2133 // Type of pointer to the array of pointers.
2134 PointerType *PtrTy =
2135 PointerType::get(C&: V.getContext(), AddressSpace: VEPT->getAddressSpace());
2136
2137 SmallVector<Constant *, 8> UsedArray;
2138 for (GlobalValue *GV : Init) {
2139 Constant *Cast = ConstantExpr::getPointerBitCastOrAddrSpaceCast(C: GV, Ty: PtrTy);
2140 UsedArray.push_back(Elt: Cast);
2141 }
2142
2143 // Sort to get deterministic order.
2144 array_pod_sort(Start: UsedArray.begin(), End: UsedArray.end(), Compare: compareNames);
2145 ArrayType *ATy = ArrayType::get(ElementType: PtrTy, NumElements: UsedArray.size());
2146
2147 Module *M = V.getParent();
2148 V.removeFromParent();
2149 GlobalVariable *NV = new GlobalVariable(
2150 *M, ATy, false, GlobalValue::AppendingLinkage,
2151 ConstantArray::get(T: ATy, V: UsedArray), "", nullptr,
2152 GlobalVariable::NotThreadLocal, V.getType()->getAddressSpace());
2153 NV->takeName(V: &V);
2154 NV->setSection("llvm.metadata");
2155 delete &V;
2156}
2157
2158namespace {
2159
2160/// An easy to access representation of llvm.used and llvm.compiler.used.
2161class LLVMUsed {
2162 SmallPtrSet<GlobalValue *, 4> Used;
2163 SmallPtrSet<GlobalValue *, 4> CompilerUsed;
2164 GlobalVariable *UsedV;
2165 GlobalVariable *CompilerUsedV;
2166
2167public:
2168 LLVMUsed(Module &M) {
2169 SmallVector<GlobalValue *, 4> Vec;
2170 UsedV = collectUsedGlobalVariables(M, Vec, CompilerUsed: false);
2171 Used = {llvm::from_range, Vec};
2172 Vec.clear();
2173 CompilerUsedV = collectUsedGlobalVariables(M, Vec, CompilerUsed: true);
2174 CompilerUsed = {llvm::from_range, Vec};
2175 }
2176
2177 using iterator = SmallPtrSet<GlobalValue *, 4>::iterator;
2178 using used_iterator_range = iterator_range<iterator>;
2179
2180 iterator usedBegin() { return Used.begin(); }
2181 iterator usedEnd() { return Used.end(); }
2182
2183 used_iterator_range used() {
2184 return used_iterator_range(usedBegin(), usedEnd());
2185 }
2186
2187 iterator compilerUsedBegin() { return CompilerUsed.begin(); }
2188 iterator compilerUsedEnd() { return CompilerUsed.end(); }
2189
2190 used_iterator_range compilerUsed() {
2191 return used_iterator_range(compilerUsedBegin(), compilerUsedEnd());
2192 }
2193
2194 bool usedCount(GlobalValue *GV) const { return Used.count(Ptr: GV); }
2195
2196 bool compilerUsedCount(GlobalValue *GV) const {
2197 return CompilerUsed.count(Ptr: GV);
2198 }
2199
2200 bool usedErase(GlobalValue *GV) { return Used.erase(Ptr: GV); }
2201 bool compilerUsedErase(GlobalValue *GV) { return CompilerUsed.erase(Ptr: GV); }
2202 bool usedInsert(GlobalValue *GV) { return Used.insert(Ptr: GV).second; }
2203
2204 bool compilerUsedInsert(GlobalValue *GV) {
2205 return CompilerUsed.insert(Ptr: GV).second;
2206 }
2207
2208 void syncVariablesAndSets() {
2209 if (UsedV)
2210 setUsedInitializer(V&: *UsedV, Init: Used);
2211 if (CompilerUsedV)
2212 setUsedInitializer(V&: *CompilerUsedV, Init: CompilerUsed);
2213 }
2214};
2215
2216} // end anonymous namespace
2217
2218static bool hasUseOtherThanLLVMUsed(GlobalAlias &GA, const LLVMUsed &U) {
2219 if (GA.use_empty()) // No use at all.
2220 return false;
2221
2222 assert((!U.usedCount(&GA) || !U.compilerUsedCount(&GA)) &&
2223 "We should have removed the duplicated "
2224 "element from llvm.compiler.used");
2225 if (!GA.hasOneUse())
2226 // Strictly more than one use. So at least one is not in llvm.used and
2227 // llvm.compiler.used.
2228 return true;
2229
2230 // Exactly one use. Check if it is in llvm.used or llvm.compiler.used.
2231 return !U.usedCount(GV: &GA) && !U.compilerUsedCount(GV: &GA);
2232}
2233
2234static bool mayHaveOtherReferences(GlobalValue &GV, const LLVMUsed &U) {
2235 if (!GV.hasLocalLinkage())
2236 return true;
2237
2238 return U.usedCount(GV: &GV) || U.compilerUsedCount(GV: &GV);
2239}
2240
2241static bool hasUsesToReplace(GlobalAlias &GA, const LLVMUsed &U,
2242 bool &RenameTarget) {
2243 if (GA.isWeakForLinker())
2244 return false;
2245
2246 RenameTarget = false;
2247 bool Ret = false;
2248 if (hasUseOtherThanLLVMUsed(GA, U))
2249 Ret = true;
2250
2251 // If the alias is externally visible, we may still be able to simplify it.
2252 if (!mayHaveOtherReferences(GV&: GA, U))
2253 return Ret;
2254
2255 // If the aliasee has internal linkage and no other references (e.g.,
2256 // @llvm.used, @llvm.compiler.used), give it the name and linkage of the
2257 // alias, and delete the alias. This turns:
2258 // define internal ... @f(...)
2259 // @a = alias ... @f
2260 // into:
2261 // define ... @a(...)
2262 Constant *Aliasee = GA.getAliasee();
2263 GlobalValue *Target = cast<GlobalValue>(Val: Aliasee->stripPointerCasts());
2264 if (mayHaveOtherReferences(GV&: *Target, U))
2265 return Ret;
2266
2267 RenameTarget = true;
2268 return true;
2269}
2270
2271static bool
2272OptimizeGlobalAliases(Module &M,
2273 SmallPtrSetImpl<const Comdat *> &NotDiscardableComdats) {
2274 bool Changed = false;
2275 LLVMUsed Used(M);
2276
2277 for (GlobalValue *GV : Used.used())
2278 Used.compilerUsedErase(GV);
2279
2280 // Return whether GV is explicitly or implicitly dso_local and not replaceable
2281 // by another definition in the current linkage unit.
2282 auto IsModuleLocal = [](GlobalValue &GV) {
2283 return !GlobalValue::isInterposableLinkage(Linkage: GV.getLinkage()) &&
2284 (GV.isDSOLocal() || GV.isImplicitDSOLocal());
2285 };
2286
2287 for (GlobalAlias &J : llvm::make_early_inc_range(Range: M.aliases())) {
2288 // Aliases without names cannot be referenced outside this module.
2289 if (!J.hasName() && !J.isDeclaration() && !J.hasLocalLinkage())
2290 J.setLinkage(GlobalValue::InternalLinkage);
2291
2292 if (deleteIfDead(GV&: J, NotDiscardableComdats)) {
2293 Changed = true;
2294 continue;
2295 }
2296
2297 // If the alias can change at link time, nothing can be done - bail out.
2298 if (!IsModuleLocal(J))
2299 continue;
2300
2301 Constant *Aliasee = J.getAliasee();
2302 GlobalValue *Target = dyn_cast<GlobalValue>(Val: Aliasee->stripPointerCasts());
2303 // We can't trivially replace the alias with the aliasee if the aliasee is
2304 // non-trivial in some way. We also can't replace the alias with the aliasee
2305 // if the aliasee may be preemptible at runtime. On ELF, a non-preemptible
2306 // alias can be used to access the definition as if preemption did not
2307 // happen.
2308 // TODO: Try to handle non-zero GEPs of local aliasees.
2309 if (!Target || !IsModuleLocal(*Target))
2310 continue;
2311
2312 Target->removeDeadConstantUsers();
2313
2314 // Make all users of the alias use the aliasee instead.
2315 bool RenameTarget;
2316 if (!hasUsesToReplace(GA&: J, U: Used, RenameTarget))
2317 continue;
2318
2319 J.replaceAllUsesWith(V: Aliasee);
2320 ++NumAliasesResolved;
2321 Changed = true;
2322
2323 if (RenameTarget) {
2324 // Give the aliasee the name, linkage and other attributes of the alias.
2325 Target->takeName(V: &J);
2326 Target->setLinkage(J.getLinkage());
2327 Target->setDSOLocal(J.isDSOLocal());
2328 Target->setVisibility(J.getVisibility());
2329 Target->setDLLStorageClass(J.getDLLStorageClass());
2330
2331 if (Used.usedErase(GV: &J))
2332 Used.usedInsert(GV: Target);
2333
2334 if (Used.compilerUsedErase(GV: &J))
2335 Used.compilerUsedInsert(GV: Target);
2336 } else if (mayHaveOtherReferences(GV&: J, U: Used))
2337 continue;
2338
2339 // Delete the alias.
2340 M.eraseAlias(Alias: &J);
2341 ++NumAliasesRemoved;
2342 Changed = true;
2343 }
2344
2345 Used.syncVariablesAndSets();
2346
2347 return Changed;
2348}
2349
2350static Function *
2351FindAtExitLibFunc(Module &M,
2352 function_ref<TargetLibraryInfo &(Function &)> GetTLI,
2353 LibFunc Func) {
2354 // Hack to get a default TLI before we have actual Function.
2355 auto FuncIter = M.begin();
2356 if (FuncIter == M.end())
2357 return nullptr;
2358 auto *TLI = &GetTLI(*FuncIter);
2359
2360 if (!TLI->has(F: Func))
2361 return nullptr;
2362
2363 Function *Fn = M.getFunction(Name: TLI->getName(F: Func));
2364 if (!Fn)
2365 return nullptr;
2366
2367 // Now get the actual TLI for Fn.
2368 TLI = &GetTLI(*Fn);
2369
2370 // Make sure that the function has the correct prototype.
2371 LibFunc F;
2372 if (!TLI->getLibFunc(FDecl: *Fn, F) || F != Func)
2373 return nullptr;
2374
2375 return Fn;
2376}
2377
2378/// Returns whether the given function is an empty C++ destructor or atexit
2379/// handler and can therefore be eliminated. Note that we assume that other
2380/// optimization passes have already simplified the code so we simply check for
2381/// 'ret'.
2382static bool IsEmptyAtExitFunction(const Function &Fn) {
2383 // FIXME: We could eliminate C++ destructors if they're readonly/readnone and
2384 // nounwind, but that doesn't seem worth doing.
2385 if (Fn.isDeclaration())
2386 return false;
2387
2388 for (const auto &I : Fn.getEntryBlock()) {
2389 if (I.isDebugOrPseudoInst())
2390 continue;
2391 if (isa<ReturnInst>(Val: I))
2392 return true;
2393 break;
2394 }
2395 return false;
2396}
2397
2398static bool OptimizeEmptyGlobalAtExitDtors(Function *CXAAtExitFn, bool isCXX) {
2399 /// Itanium C++ ABI p3.3.5:
2400 ///
2401 /// After constructing a global (or local static) object, that will require
2402 /// destruction on exit, a termination function is registered as follows:
2403 ///
2404 /// extern "C" int __cxa_atexit ( void (*f)(void *), void *p, void *d );
2405 ///
2406 /// This registration, e.g. __cxa_atexit(f,p,d), is intended to cause the
2407 /// call f(p) when DSO d is unloaded, before all such termination calls
2408 /// registered before this one. It returns zero if registration is
2409 /// successful, nonzero on failure.
2410
2411 // This pass will look for calls to __cxa_atexit or atexit where the function
2412 // is trivial and remove them.
2413 bool Changed = false;
2414
2415 for (User *U : llvm::make_early_inc_range(Range: CXAAtExitFn->users())) {
2416 // We're only interested in calls. Theoretically, we could handle invoke
2417 // instructions as well, but neither llvm-gcc nor clang generate invokes
2418 // to __cxa_atexit.
2419 CallInst *CI = dyn_cast<CallInst>(Val: U);
2420 if (!CI)
2421 continue;
2422
2423 Function *DtorFn =
2424 dyn_cast<Function>(Val: CI->getArgOperand(i: 0)->stripPointerCasts());
2425 if (!DtorFn || !IsEmptyAtExitFunction(Fn: *DtorFn))
2426 continue;
2427
2428 // Just remove the call.
2429 CI->replaceAllUsesWith(V: Constant::getNullValue(Ty: CI->getType()));
2430 CI->eraseFromParent();
2431
2432 if (isCXX)
2433 ++NumCXXDtorsRemoved;
2434 else
2435 ++NumAtExitRemoved;
2436
2437 Changed |= true;
2438 }
2439
2440 return Changed;
2441}
2442
2443static Function *hasSideeffectFreeStaticResolution(GlobalIFunc &IF) {
2444 if (IF.isInterposable())
2445 return nullptr;
2446
2447 Function *Resolver = IF.getResolverFunction();
2448 if (!Resolver)
2449 return nullptr;
2450
2451 if (Resolver->isInterposable())
2452 return nullptr;
2453
2454 // Only handle functions that have been optimized into a single basic block.
2455 auto It = Resolver->begin();
2456 if (++It != Resolver->end())
2457 return nullptr;
2458
2459 BasicBlock &BB = Resolver->getEntryBlock();
2460
2461 if (any_of(Range&: BB, P: [](Instruction &I) { return I.mayHaveSideEffects(); }))
2462 return nullptr;
2463
2464 auto *Ret = dyn_cast<ReturnInst>(Val: BB.getTerminator());
2465 if (!Ret)
2466 return nullptr;
2467
2468 return dyn_cast<Function>(Val: Ret->getReturnValue());
2469}
2470
2471/// Find IFuncs that have resolvers that always point at the same statically
2472/// known callee, and replace their callers with a direct call.
2473static bool OptimizeStaticIFuncs(Module &M) {
2474 bool Changed = false;
2475 for (GlobalIFunc &IF : M.ifuncs())
2476 if (Function *Callee = hasSideeffectFreeStaticResolution(IF))
2477 if (!IF.use_empty() &&
2478 (!Callee->isDeclaration() ||
2479 none_of(Range: IF.users(), P: [](User *U) { return isa<GlobalAlias>(Val: U); }))) {
2480 IF.replaceAllUsesWith(V: Callee);
2481 NumIFuncsResolved++;
2482 Changed = true;
2483 }
2484 return Changed;
2485}
2486
2487static bool
2488DeleteDeadIFuncs(Module &M,
2489 SmallPtrSetImpl<const Comdat *> &NotDiscardableComdats) {
2490 bool Changed = false;
2491 for (GlobalIFunc &IF : make_early_inc_range(Range: M.ifuncs()))
2492 if (deleteIfDead(GV&: IF, NotDiscardableComdats)) {
2493 NumIFuncsDeleted++;
2494 Changed = true;
2495 }
2496 return Changed;
2497}
2498
2499// Follows the use-def chain of \p V backwards until it finds a Function,
2500// in which case it collects in \p Versions. Return true on successful
2501// use-def chain traversal, false otherwise.
2502static bool
2503collectVersions(Value *V, SmallVectorImpl<Function *> &Versions,
2504 function_ref<TargetTransformInfo &(Function &)> GetTTI) {
2505 if (auto *F = dyn_cast<Function>(Val: V)) {
2506 if (!GetTTI(*F).isMultiversionedFunction(F: *F))
2507 return false;
2508 Versions.push_back(Elt: F);
2509 } else if (auto *Sel = dyn_cast<SelectInst>(Val: V)) {
2510 if (!collectVersions(V: Sel->getTrueValue(), Versions, GetTTI))
2511 return false;
2512 if (!collectVersions(V: Sel->getFalseValue(), Versions, GetTTI))
2513 return false;
2514 } else if (auto *Phi = dyn_cast<PHINode>(Val: V)) {
2515 for (unsigned I = 0, E = Phi->getNumIncomingValues(); I != E; ++I)
2516 if (!collectVersions(V: Phi->getIncomingValue(i: I), Versions, GetTTI))
2517 return false;
2518 } else {
2519 // Unknown instruction type. Bail.
2520 return false;
2521 }
2522 return true;
2523}
2524
2525// Try to statically resolve calls to versioned functions when possible. First
2526// we identify the function versions which are associated with an IFUNC symbol.
2527// We do that by examining the resolver function of the IFUNC. Once we have
2528// collected all the function versions, we sort them in decreasing priority
2529// order. This is necessary for determining the most suitable callee version
2530// for each caller version. We then collect all the callsites to versioned
2531// functions. The static resolution is performed by comparing the feature sets
2532// between callers and callees. Specifically:
2533// * Start a walk over caller and callee lists simultaneously in order of
2534// decreasing priority.
2535// * Statically resolve calls from the current caller to the current callee,
2536// iff the caller feature bits are a superset of the callee feature bits.
2537// * For FMV callers, as long as the caller feature bits are a subset of the
2538// callee feature bits, advance to the next callee. This effectively prevents
2539// considering the current callee as a candidate for static resolution by
2540// following callers (explanation: preceding callers would not have been
2541// selected in a hypothetical runtime execution).
2542// * Advance to the next caller.
2543//
2544// Presentation in EuroLLVM2025:
2545// https://www.youtube.com/watch?v=k54MFimPz-A&t=867s
2546static bool OptimizeNonTrivialIFuncs(
2547 Module &M, function_ref<TargetTransformInfo &(Function &)> GetTTI) {
2548 bool Changed = false;
2549
2550 // Map containing the feature bits for a given function.
2551 DenseMap<Function *, APInt> FeatureMask;
2552 // Map containing the priority bits for a given function.
2553 DenseMap<Function *, APInt> PriorityMask;
2554 // Map containing all the function versions corresponding to an IFunc symbol.
2555 DenseMap<GlobalIFunc *, SmallVector<Function *>> VersionedFuncs;
2556 // Map containing the IFunc symbol a function is version of.
2557 DenseMap<Function *, GlobalIFunc *> VersionOf;
2558 // List of all the interesting IFuncs found in the module.
2559 SmallVector<GlobalIFunc *> IFuncs;
2560
2561 for (GlobalIFunc &IF : M.ifuncs()) {
2562 LLVM_DEBUG(dbgs() << "Examining IFUNC " << IF.getName() << "\n");
2563
2564 if (IF.isInterposable())
2565 continue;
2566
2567 Function *Resolver = IF.getResolverFunction();
2568 if (!Resolver)
2569 continue;
2570
2571 if (Resolver->isInterposable())
2572 continue;
2573
2574 SmallVector<Function *> Versions;
2575 // Discover the versioned functions.
2576 if (any_of(Range&: *Resolver, P: [&](BasicBlock &BB) {
2577 if (auto *Ret = dyn_cast_or_null<ReturnInst>(Val: BB.getTerminator()))
2578 if (!collectVersions(V: Ret->getReturnValue(), Versions, GetTTI))
2579 return true;
2580 return false;
2581 }))
2582 continue;
2583
2584 if (Versions.empty())
2585 continue;
2586
2587 for (Function *V : Versions) {
2588 VersionOf.insert(KV: {V, &IF});
2589 auto [FeatIt, FeatInserted] = FeatureMask.try_emplace(Key: V);
2590 if (FeatInserted)
2591 FeatIt->second = GetTTI(*V).getFeatureMask(F: *V);
2592 auto [PriorIt, PriorInserted] = PriorityMask.try_emplace(Key: V);
2593 if (PriorInserted)
2594 PriorIt->second = GetTTI(*V).getPriorityMask(F: *V);
2595 }
2596
2597 // Sort function versions in decreasing priority order.
2598 sort(C&: Versions, Comp: [&](auto *LHS, auto *RHS) {
2599 return PriorityMask[LHS].ugt(PriorityMask[RHS]);
2600 });
2601
2602 IFuncs.push_back(Elt: &IF);
2603 VersionedFuncs.try_emplace(Key: &IF, Args: std::move(Versions));
2604 }
2605
2606 for (GlobalIFunc *CalleeIF : IFuncs) {
2607 SmallVector<Function *> NonFMVCallers;
2608 DenseSet<GlobalIFunc *> CallerIFuncs;
2609 DenseMap<Function *, SmallVector<CallBase *>> CallSites;
2610
2611 // Find the callsites.
2612 for (User *U : CalleeIF->users()) {
2613 if (auto *CB = dyn_cast<CallBase>(Val: U)) {
2614 if (CB->getCalledOperand() == CalleeIF) {
2615 Function *Caller = CB->getFunction();
2616 GlobalIFunc *CallerIF = nullptr;
2617 TargetTransformInfo &TTI = GetTTI(*Caller);
2618 bool CallerIsFMV = TTI.isMultiversionedFunction(F: *Caller);
2619 // The caller is a version of a known IFunc.
2620 if (auto It = VersionOf.find(Val: Caller); It != VersionOf.end())
2621 CallerIF = It->second;
2622 else if (!CallerIsFMV && OptimizeNonFMVCallers) {
2623 // The caller is non-FMV.
2624 auto [It, Inserted] = FeatureMask.try_emplace(Key: Caller);
2625 if (Inserted)
2626 It->second = TTI.getFeatureMask(F: *Caller);
2627 } else
2628 // The caller is none of the above, skip.
2629 continue;
2630 auto [It, Inserted] = CallSites.try_emplace(Key: Caller);
2631 if (Inserted) {
2632 if (CallerIsFMV)
2633 CallerIFuncs.insert(V: CallerIF);
2634 else
2635 NonFMVCallers.push_back(Elt: Caller);
2636 }
2637 It->second.push_back(Elt: CB);
2638 }
2639 }
2640 }
2641
2642 if (CallSites.empty())
2643 continue;
2644
2645 LLVM_DEBUG(dbgs() << "Statically resolving calls to function "
2646 << CalleeIF->getResolverFunction()->getName() << "\n");
2647
2648 // The complexity of this algorithm is linear: O(NumCallers + NumCallees)
2649 // if NumCallers > MaxIFuncVersions || NumCallees > MaxIFuncVersions,
2650 // otherwise it is cubic: O((NumCallers ^ 2) x NumCallees).
2651 auto staticallyResolveCalls = [&](ArrayRef<Function *> Callers,
2652 ArrayRef<Function *> Callees,
2653 bool CallerIsFMV) {
2654 bool AllowExpensiveChecks = CallerIsFMV &&
2655 Callers.size() <= MaxIFuncVersions &&
2656 Callees.size() <= MaxIFuncVersions;
2657 // Index to the highest callee candidate.
2658 unsigned J = 0;
2659
2660 for (unsigned I = 0, E = Callers.size(); I < E; ++I) {
2661 // There are no callee candidates left.
2662 if (J == Callees.size())
2663 break;
2664
2665 Function *Caller = Callers[I];
2666 APInt CallerBits = FeatureMask[Caller];
2667
2668 // Compare the feature bits of the best callee candidate with all the
2669 // caller versions preceeding the current one. For each prior caller
2670 // discard feature bits that are known to be available in the current
2671 // caller. As long as the known missing feature bits are a subset of the
2672 // callee feature bits, advance to the next callee and start over.
2673 auto eliminateAvailableFeatures = [&](unsigned BestCandidate) {
2674 unsigned K = 0;
2675 while (K < I && BestCandidate < Callees.size()) {
2676 APInt MissingBits = FeatureMask[Callers[K]] & ~CallerBits;
2677 if (MissingBits.isSubsetOf(RHS: FeatureMask[Callees[BestCandidate]])) {
2678 ++BestCandidate;
2679 // Start over.
2680 K = 0;
2681 } else
2682 ++K;
2683 }
2684 return BestCandidate;
2685 };
2686
2687 unsigned BestCandidate =
2688 AllowExpensiveChecks ? eliminateAvailableFeatures(J) : J;
2689 // No callee candidate was found for this caller.
2690 if (BestCandidate == Callees.size())
2691 continue;
2692
2693 LLVM_DEBUG(dbgs() << " Examining "
2694 << (CallerIsFMV ? "FMV" : "regular") << " caller "
2695 << Caller->getName() << "\n");
2696
2697 Function *Callee = Callees[BestCandidate];
2698 APInt CalleeBits = FeatureMask[Callee];
2699
2700 // Statically resolve calls from the current caller to the current
2701 // callee, iff the caller feature bits are a superset of the callee
2702 // feature bits.
2703 if (CalleeBits.isSubsetOf(RHS: CallerBits)) {
2704 // Not all caller versions are necessarily users of the callee IFUNC.
2705 if (auto It = CallSites.find(Val: Caller); It != CallSites.end()) {
2706 for (CallBase *CS : It->second) {
2707 LLVM_DEBUG(dbgs() << " Redirecting call " << Caller->getName()
2708 << " -> " << Callee->getName() << "\n");
2709 CS->setCalledOperand(Callee);
2710 }
2711 Changed = true;
2712 }
2713 }
2714
2715 // Nothing else to do about non-FMV callers.
2716 if (!CallerIsFMV)
2717 continue;
2718
2719 // For FMV callers, as long as the caller feature bits are a subset of
2720 // the callee feature bits, advance to the next callee. This effectively
2721 // prevents considering the current callee as a candidate for static
2722 // resolution by following callers.
2723 while (CallerBits.isSubsetOf(RHS: FeatureMask[Callees[J]]) &&
2724 ++J < Callees.size())
2725 ;
2726 }
2727 };
2728
2729 auto &Callees = VersionedFuncs[CalleeIF];
2730
2731 // Optimize non-FMV calls.
2732 if (OptimizeNonFMVCallers)
2733 staticallyResolveCalls(NonFMVCallers, Callees, /*CallerIsFMV=*/false);
2734
2735 // Optimize FMV calls.
2736 for (GlobalIFunc *CallerIF : CallerIFuncs) {
2737 auto &Callers = VersionedFuncs[CallerIF];
2738 staticallyResolveCalls(Callers, Callees, /*CallerIsFMV=*/true);
2739 }
2740
2741 if (CalleeIF->use_empty() ||
2742 all_of(Range: CalleeIF->users(), P: [](User *U) { return isa<GlobalAlias>(Val: U); }))
2743 NumIFuncsResolved++;
2744 }
2745 return Changed;
2746}
2747
2748static bool
2749optimizeGlobalsInModule(Module &M, const DataLayout &DL,
2750 function_ref<TargetLibraryInfo &(Function &)> GetTLI,
2751 function_ref<TargetTransformInfo &(Function &)> GetTTI,
2752 function_ref<BlockFrequencyInfo &(Function &)> GetBFI,
2753 function_ref<DominatorTree &(Function &)> LookupDomTree,
2754 function_ref<void(Function &F)> ChangedCFGCallback,
2755 function_ref<void(Function &F)> DeleteFnCallback) {
2756 SmallPtrSet<const Comdat *, 8> NotDiscardableComdats;
2757 bool Changed = false;
2758 bool LocalChange = true;
2759 std::optional<uint32_t> FirstNotFullyEvaluatedPriority;
2760
2761 while (LocalChange) {
2762 LocalChange = false;
2763
2764 NotDiscardableComdats.clear();
2765 for (const GlobalVariable &GV : M.globals())
2766 if (const Comdat *C = GV.getComdat())
2767 if (!GV.isDiscardableIfUnused() || !GV.use_empty())
2768 NotDiscardableComdats.insert(Ptr: C);
2769 for (Function &F : M)
2770 if (const Comdat *C = F.getComdat())
2771 if (!F.isDefTriviallyDead())
2772 NotDiscardableComdats.insert(Ptr: C);
2773 for (GlobalAlias &GA : M.aliases())
2774 if (const Comdat *C = GA.getComdat())
2775 if (!GA.isDiscardableIfUnused() || !GA.use_empty())
2776 NotDiscardableComdats.insert(Ptr: C);
2777
2778 // Delete functions that are trivially dead, ccc -> fastcc
2779 LocalChange |= OptimizeFunctions(M, GetTLI, GetTTI, GetBFI, LookupDomTree,
2780 NotDiscardableComdats, ChangedCFGCallback,
2781 DeleteFnCallback);
2782
2783 // Optimize global_ctors list.
2784 LocalChange |=
2785 optimizeGlobalCtorsList(M, ShouldRemove: [&](uint32_t Priority, Function *F) {
2786 if (FirstNotFullyEvaluatedPriority &&
2787 *FirstNotFullyEvaluatedPriority != Priority)
2788 return false;
2789 bool Evaluated = EvaluateStaticConstructor(F, DL, TLI: &GetTLI(*F));
2790 if (!Evaluated)
2791 FirstNotFullyEvaluatedPriority = Priority;
2792 return Evaluated;
2793 });
2794
2795 // Optimize non-address-taken globals.
2796 LocalChange |= OptimizeGlobalVars(M, GetTTI, GetTLI, LookupDomTree,
2797 NotDiscardableComdats);
2798
2799 // Resolve aliases, when possible.
2800 LocalChange |= OptimizeGlobalAliases(M, NotDiscardableComdats);
2801
2802 // Try to remove trivial global destructors if they are not removed
2803 // already.
2804 if (Function *CXAAtExitFn =
2805 FindAtExitLibFunc(M, GetTLI, Func: LibFunc_cxa_atexit))
2806 LocalChange |= OptimizeEmptyGlobalAtExitDtors(CXAAtExitFn, isCXX: true);
2807
2808 if (Function *AtExitFn = FindAtExitLibFunc(M, GetTLI, Func: LibFunc_atexit))
2809 LocalChange |= OptimizeEmptyGlobalAtExitDtors(CXAAtExitFn: AtExitFn, isCXX: false);
2810
2811 // Optimize IFuncs whose callee's are statically known.
2812 LocalChange |= OptimizeStaticIFuncs(M);
2813
2814 // Optimize IFuncs based on the target features of the caller.
2815 LocalChange |= OptimizeNonTrivialIFuncs(M, GetTTI);
2816
2817 // Remove any IFuncs that are now dead.
2818 LocalChange |= DeleteDeadIFuncs(M, NotDiscardableComdats);
2819
2820 Changed |= LocalChange;
2821 }
2822
2823 // TODO: Move all global ctors functions to the end of the module for code
2824 // layout.
2825
2826 return Changed;
2827}
2828
2829PreservedAnalyses GlobalOptPass::run(Module &M, ModuleAnalysisManager &AM) {
2830 auto &DL = M.getDataLayout();
2831 auto &FAM =
2832 AM.getResult<FunctionAnalysisManagerModuleProxy>(IR&: M).getManager();
2833 auto LookupDomTree = [&FAM](Function &F) -> DominatorTree &{
2834 return FAM.getResult<DominatorTreeAnalysis>(IR&: F);
2835 };
2836 auto GetTLI = [&FAM](Function &F) -> TargetLibraryInfo & {
2837 return FAM.getResult<TargetLibraryAnalysis>(IR&: F);
2838 };
2839 auto GetTTI = [&FAM](Function &F) -> TargetTransformInfo & {
2840 return FAM.getResult<TargetIRAnalysis>(IR&: F);
2841 };
2842
2843 auto GetBFI = [&FAM](Function &F) -> BlockFrequencyInfo & {
2844 return FAM.getResult<BlockFrequencyAnalysis>(IR&: F);
2845 };
2846 auto ChangedCFGCallback = [&FAM](Function &F) {
2847 FAM.invalidate(IR&: F, PA: PreservedAnalyses::none());
2848 };
2849 auto DeleteFnCallback = [&FAM](Function &F) { FAM.clear(IR&: F, Name: F.getName()); };
2850
2851 if (!optimizeGlobalsInModule(M, DL, GetTLI, GetTTI, GetBFI, LookupDomTree,
2852 ChangedCFGCallback, DeleteFnCallback))
2853 return PreservedAnalyses::all();
2854
2855 PreservedAnalyses PA = PreservedAnalyses::none();
2856 // We made sure to clear analyses for deleted functions.
2857 PA.preserve<FunctionAnalysisManagerModuleProxy>();
2858 // The only place we modify the CFG is when calling
2859 // removeUnreachableBlocks(), but there we make sure to invalidate analyses
2860 // for modified functions.
2861 PA.preserveSet<CFGAnalyses>();
2862 return PA;
2863}
2864